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The influence of ambient temperature on Horned Lark incubation behaviour in an alpine environment

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Abstract

Incubation is an energetically costly activity for birds, and may be particularly challenging in alpine environments where ambient temperatures are typically low but can fluctuate widely. Little is known about how incubating birds respond to cold temperatures such as those that occur in alpine environments. We measured incubation rhythms in horned larks (Eremophila alpestris) breeding in alpine tundra in British Columbia and found quadratic relationships between ambient temperature and the total time spent incubating, the frequency of recesses, and on-bout duration. Females spent less time on the nest as ambient temperature increased to 12-13°C; at higher temperatures the relationship was reversed. They adjusted the amount of time incubating by varying the frequency rather than duration of recesses. It appears that female horned larks in alpine environments modify their behaviour so as to minimize the cost of rewarming eggs and the risk of cooling the eggs. The ability of horned larks to maintain high levels of nest attentiveness at low ambient temperatures suggests that they are well adapted to the degree of environmental variation they currently experience in alpine environments and that they may compensate for the shorter breeding seasons and reduced re-nesting opportunities by increasing parental investment.

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... Ambient temperature is one of the main factors determining parental allocation of time between incubation (on-bout) and foraging (off-bout) (Conway & Martin 2000a). Species breeding in high elevation areas, for example, vary incubation behaviour to cope with low ambient temperatures (Martin & Wiebe 2004) by increasing nest attentiveness (Camfield & Martin 2009) and decreasing the length of incubation bouts (Kovařík et al. 2009) and off-bout periods (MacDonald et al. 2014). Incubation rhythm of females may vary with date, time of day and incubation stage, which affect the energetic needs of the parents (Camfield & Martin 2009, Kovařík et al. 2009, Endo & Ueda 2016. ...
... Species breeding in high elevation areas, for example, vary incubation behaviour to cope with low ambient temperatures (Martin & Wiebe 2004) by increasing nest attentiveness (Camfield & Martin 2009) and decreasing the length of incubation bouts (Kovařík et al. 2009) and off-bout periods (MacDonald et al. 2014). Incubation rhythm of females may vary with date, time of day and incubation stage, which affect the energetic needs of the parents (Camfield & Martin 2009, Kovařík et al. 2009, Endo & Ueda 2016. Parent birds may, therefore, show two main strategies for coping with changes in environmental conditions and their own energetic demands. ...
... For each two-hour period from 07:00 to 19:00 hours, we computed: (1) nest attentiveness, as the proportion of time that the female spent on the nest; (2) mean on-bout duration, as the mean duration of incubation bouts, (3) mean off-bout duration, as the mean duration of bouts that the female spent off the nest and (4) off-bout frequency, as the number of times that the female left the nest (Camfield & Martin 2009). We also computed mean ambient temperature for each two-hour period. ...
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Capsule: The incubation behaviour of the Fire-tailed Sunbird Aethopyga ignicauda was measured using data loggers in the Hengduan Mountains, China, to test predictions of parental trade-off theory. Overall, female sunbirds prioritized incubation rather than self-feeding when temperatures were lowest, suggesting that brood demands may dominate parental behaviour in climatically extreme environments.
... However, incubation behavior is often neglected as a method for investigating relationships between animals and their environment for conservation and many of their survival strategies and adaptations (Spiegel et al. 2012). Most studies of incubation rhythms in birds have been conducted in moderate environments (Camfield and Martin 2009) and studies under alpine environments have focused mainly on uniparental incubators. However, the situation in species with biparental incubation is more complex due to the potentially different responses of each parent to changes in the cost of incubation (Smith et al. 2012). ...
... To control for repeated measures of incubation behaviors at a given nest, we included nest identity as a random effect. Year (2014 and2015), date, days of incubation and time of day were also added as fixed effects since they might potentially influence the incubation behavior (Camfield and Martin 2009). Partner's behavior was also a fixed factor, and partner's behavior × time period interaction was included to determine if the relationship between the incubating crane's behaviors on the nest and partner's behaviors varied over time. ...
... The highest female nest attendance was from 06:30 to 08:29 h, when females may be short of energy after an overnight incubation. This finding is similar to the incubation behavior during early morning for females of a uniparental species Horned Lark (Eremophila alpestris) breeding in alpine tundr (Camfield and Martin 2009), but was in contrast to the uniparental incubation pattern for the female King Eider, which took more recesses at low temperatures because recesses were driven by metabolic expenses and local foraging conditions (Bentzen et al. 2010). Our study demonstrated that female Black-necked Cranes shifted priority between self-maintenance and incubation demands depending on various temperature conditions and their parental cooperation. ...
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Background: The behavior of cranes reflects many of their survival strategies, but little has been known of the incubation strategies of cranes, in which both parents share incubation duties, in response to cold temperatures in alpine environments. The lack of information may restrict the effective conservation of the threatened Black-necked Crane (Grus nigricollis), a biparental bird nesting in high elevation wetlands. Methods: We directly observed and used infrared video cameras from 2014 to 2015 to study the incubation behavior and quantitatively measured the frequency and details of egg turning behavior in the Black-necked Crane at the Yanchiwan National Nature Reserve in western Gansu Province, China. Results: At lower ambient temperatures in the morning, crane parents spent more time on the nest with less recess frequency and prolonged on-bout duration, while at higher temperatures around noon, the parents had more frequent recesses from incubation and shorter periods between nest exchanges. They adjusted the amount of time incubating by varying the recess frequency and the length of on-bout duration. Mean nest attendance and egg turning frequency of females were significantly higher than those of the males. The nest attendance and on-bout duration of females showed a significantly negative relationship with those of males. The two parents responded differently to the change of temperature. Females spent more time on the nest at lower morning temperatures, while males increased their time on the nest at higher temperatures after noon. Higher incubation recess frequency and egg turning frequency were observed at noon, probably because parents spent more time foraging, taking advantage of the lower egg cooling rate. Conclusion: Both Black-necked Crane parents in the alpine environment adjusted their behavior in response to the thermal requirements of eggs and the weather conditions experienced. Our findings demonstrate that parents of this species incubated in different but complementary ways and efficiently enhanced egg care in a dynamic environment, so as to maximize benefits from the warm portion of the day and the intense solar radiation while minimizing the cost of rewarming eggs and the risks of cooling eggs.
... In dieser Studie untersuchten wir, in wie weit männliche Partnerfütterung die weibliche Nestanwesenheit in Blaumeisen (Cyanistes caeruleus) beeinflusst und ob sich dies auf die Introduction Incubation is a key factor of avian parental care and requires a substantial energetic investment by the incubating individuals (e.g. Camfield and Martin 2009;Bulla et al. 2015). To optimize embryo development, the parents have to ensure that the eggs are kept within appropriate temperature limits (Yom-Tov et al. 1978;Reid et al. 1999Reid et al. , 2000Stein et al. 2010). ...
... A common system that has been adopted by several species, possibly as a resolution to this trade-off, is a uniparental incubation system in which only the female incubates while the male provides aid in the form of supplying food ('male incubation feeding' ;Kluijver 1950;Hałupka 1994;Matysioková and Remeš 2010;Stein et al. 2010). The ''female nutrition'' hypothesis (Royama 1966) is one of the most invoked theories in this context and states that male incubation feeding enables the female to increase the amount of time she can spend incubating (female nest attendance; Royama 1966;Camfield and Martin 2009;Matysioková et al. 2011;Stein et al. 2010;Ibáñez-Á lamo and Soler 2012). Hence, in order to understand avian reproductive strategies, it is important to understand the interplay between female nest attendance and male incubation feeding and the underlying factors that drive variation in these behaviours. ...
... If male incubation feeding affects female nest attendance, this variation may be explained by variation in the circumstances that affect the need for incubation. For example, environmental factors, such as (seasonal changes in) ambient temperature (Webb 1987;Hatchwell et al. 1999;Camfield and Martin 2009;Matysioková and Remeš 2010) may affect the rate at which the eggs cool down and require females to incubate more. In addition, characteristics of the clutch, such as number of eggs, may be correlated with male incubation feeding: females with a larger clutch may require more energy to incubate the eggs or may spend more time on incubation and less on foraging (de Heij et al. 2007), so that males may need to feed females incubating larger clutches more frequently. ...
Article
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The incubation of eggs plays a key role in avian parental care. To ensure embryo development, incubating parents have to keep their eggs within the appropriate temperature limits. To do so, incubating individuals allocate substantial energy to the thermal demands of their eggs, but they face a trade-off with self-maintenance (own metabolism) because they usually cannot forage while incubating eggs. In species with female-only incubation, males can help their partners by providing them with food on the nest, a behavior which may enable females to spend more time incubating and could, consequently, lead to improved reproductive performance. In the study reported here, we first investigated whether incubation feeding by males affects nest attendance by females in Blue Tits (Cyanistes caeruleus) and subsequently determined how this incubation feeding affects reproductive performance. We found that the female nest attendance tended to increase with increasing amounts of food supplied by their male partner. Thus, males may enable females to incubate more when needed, as suggested by our observation that male incubation feeding was more frequent when the ambient temperature was lower, and especially so when females incubated later in the breeding season (during the study period the ambient temperature decreased rapidly over the breeding season, which is exceptional). Although female nest attendance did not result in a shorter time until the eggs hatched or in higher hatching success, females that attended the nest more produced heavier nestlings. We suggest that the trade-off between self-maintenance and meeting the demands of egg incubation likely tends to be less when females received more assistance from their partner during the egg incubation period, resulting in a higher investment in offspring.
... Thus in the mornings, it may be most difficult to keep eggs above critical temperatures (Drent 1975, Olson et al. 2006) and above the physiological zero temperature (PZT) of 25-27 8C below which embryogenic development is arrested (White and Kinney 1974). External temperature, nest insulation, egg size, and nest attentiveness (on-bout duration, off-bout duration and frequency) play decisive roles in determining egg temperatures (Drent 1975), and other high elevation species in cold environments show temperature-mediated trade-offs between incubation and foraging (Camfield and Martin 2009, Kovařík et al. 2009, MacDonald et al. 2013. These species tend to show high attentiveness in the cold mornings, which decreases as the day warms. ...
... These species tend to show high attentiveness in the cold mornings, which decreases as the day warms. But within the cold mornings, colder temperatures can force birds to spend more time on the nest (Camfield andMartin 2009, MacDonald et al. 2013) to prevent exposing eggs to extreme temperatures during foraging trips. We observed a strikingly different incubation rhythm in our focal nest: in the cold mornings, attentiveness was lowest as off-bouts were most frequent (Fig. 2) and the female foraged instead of incubating. ...
... C; Fig. 3). If their model applies, this suggests that PZT for C. t. omissa appears closer to 15.78 C than 268 C. Similar to other alpine birds, the slope and strength of the relationship between external temperature and on-bout duration decreased over the day as it warmed (Camfield andMartin 2009, Kovařík et al. 2009). Morning external temperatures were consistently below physiological zero and likely well below the lower bound of the thermoneutral zone (TNZ). ...
Article
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We present the first detailed nesting biology information for the highland Andean hummingbird Gould’s Inca (Coeligena torquata omissa) at 2,200–3,000 m in Manu National Park, SE Peru. We found nine mossy cup-shaped nests lined with red fern scales containing nestlings or 1–2 synchronously hatching eggs. We obtained 17 days of internal nest temperatures from one nest, which exhibited wide circadian variation (range: 14.9–36.2 8C). We show that C. t. omissa meets the challenges of life and incubation at high altitudes by undertaking numerous (20.3 +- 0.4 trips/morning, range: 14–27) and short morning off-bouts (5.2 +- 0.2 min, range: 1–24 min). In the morning, the focal bird warmed the nest 1.7 times faster than in the afternoon where incubation bouts are long (17.8 +- 0.6 min, range: 4–56) and less frequent (10.2 6 0.3 trips/afternoon). Incubation off-bout frequency and durations were not influenced by external temperature, suggesting strong nest insulation. On-bout durations increased with external temperature most strongly in the cold mornings. Short off-bouts and long on-bouts yielded high attentiveness (70.2%). One nestling fledged after 23 days. The eggs measured 15.2 6 0.4 mm by 9.3 +- 0.3 mm and weighed 0.75 +- 0.03 g (n: 12). The small mossy cup nest was 81.9 +- 5.9 mm by 75.8 +- 4.4 mm wide and 73.1 +- 6.7 mm high. The inner cup was 45.7 +- 3.0 mm long by 45.6 +- 4.1 mm wide and 30.9 +- 2.5 mm deep (n : 8). Compared to C. t. torquata, we found a smaller egg width, higher nest placement and different nest substrate, but confirmed similarities in many aspects of nesting strategies.
... Given the potential conflicting effects on both embryos and parents, ambient temperature should influence incubation behavior. A relationship between incubation rhythms and temperature has been demonstrated in several species across various habitats (Conway and Martin 2000a, Londono et al. 2008, Camfield and Martin 2009, Kovarik et al. 2009). Conway and Martin (2000a) proposed a nonlinear framework for how recess and on-bout duration of small-bodied intermittent incubators should change with ambient temperature, finding support for their hypothesis in observations of Orange-crowned Warblers (Oreothlypis celata) in Arizona, USA. ...
... Horned Larks (Eremophila alpestris) are small-bodied (28-40 g), ground-nesting passerines exhibiting femaleonly intermittent incubation with no evidence of male incubation feeding (Beason 1995 (Camfield 2008, MacDonald 2012. Birds breeding at this site face fluctuating daily temperatures, dropping to near or below freezing every night and sometimes reaching over 408C during the day (Camfield and Martin 2009). High winds, heavy fog, and storms are common during the breeding season. ...
... We used program Rhythm 1.0 (Cooper and Mills 2005) to select incubation recesses from nest temperature recordings. We considered an observation a recess if the nest temperature dropped by more than 38C for at least 3 min (following Camfield and Martin 2009). We then visually inspected the data using Raven Pro 1.3 to confirm the recesses selected by Rhythm 1.0 and manually selected any recesses that Rhythm 1.0 had not chosen but were also incubation off-bouts (i.e. a steep temperature drop lasting slightly less than 3 min). ...
Article
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Small-bodied birds engaging in incubation by a single sex experience a tradeoff between incubating to create a buffered thermal environment for their eggs and foraging to meet their own energetic requirements. This tradeoff is intensified in alpine environments, which are characterized by cold and variable conditions. We monitored the incubation rhythms of alpine Horned Larks (Eremophila alpestris) in British Columbia, Canada, across different annual thermal regimes (2005: moderate; 2006: warm; 2010: cold overnight; 2011: cold during the day). In this species, females. alone incubated and left their nests to forage at dawn, following 7 hr of nighttime incubation in near-freezing conditions. However, with early morning ambient temperatures still <5 degrees C, this placed embryos at high risk of chilling during incubation recesses. Focusing on behavioral decisions made by females at dawn (06:00-08:00 hours), we examined relationships between incubation rhythms and ambient temperature among years for evidence of variable responses to temperature. In all years, females spent more time off the nest at dawn in warmer temperatures, but in 2010, which was colder overnight, the slope of the line relating attentiveness to ambient temperature was steeper, indicating that females left their nests at colder temperatures compared with other years. In 2010 females also took shorter recesses at cold temperatures. Hatching success remained high in 2010 relative to warm or moderate years; however, overwinter survival of females declined to 48% from 2010 to 2011 compared with 72% in earlier years. When faced with exceptional thermal constraints, alpine Horned Larks made behavioral adjustments to their incubation rhythms and were able to maintain fecundity. However, potential survival costs to females implies a shift in balance of the parent-offspring tradeoff, revealing limits to coping mechanisms of alpine-breeding Horned Larks.
... We modeled two response variables separately: proportion of time off the nest and number of off-bouts within 12-hr periods and included treatment type and nest fate as fixed effects and nest ID as a random factor to account for repeated sampling of individual nests. Because nest incubation patterns can potentially vary as a function of ambient temperature, time of day (day/night), and stage in the incubation cycle (nest age; Wiebe and Martin 1998, Camfield and Martin 2009, Ricklefs and Brawn 2012, we included these variables as fixed effects. Only one of the 20 nests that we monitored was known to be a second nesting attempt (i.e., a renest). ...
... For example, we found that proportion of time off the nest for Lapland Longspurs decreased with incubation day, while the number of off-bouts stayed the same, in both treatment and control plots. A decrease in proportion of time off nest as incubation period advances is consistent with incubation behavior of other ground-nesting birds such as Horned Lark (Camfield and Martin 2009) and White-tailed Ptarmigan (Lagopus leucura; Wiebe and Martin 1997) and could be used as a tactic to avoid being detected by predators (Meyer et al. 2020) or to avoid chilling of the eggs (Olson et al. 2006). Time of day had the greatest influence on incubation behavior for both length and duration of incubation recesses, with fewer and short lengths of off-bouts occurring at night compared to during the day, despite the 24-h daylight in our study area. ...
... Altai Fescue Alpine zones (MacKenzie 2006), and as such is relatively wet, with several oligotrophic alpine lakes that persist throughout the season. This habitat is characterized by high winds and temperatures that can fluctuate from -5 to +35 °C in a single day (Camfield and Martin 2009 shorter than low elevation populations (Camfield et al. 2010; Figure 1.3). ...
... Ground-nesting, open-cup species in these habitats may be most constrained by the environment given frequent exposure to ambient conditions and predation risk Ghalambor 1999, de Zwaan and. We studied an alpine population of a ground-nesting songbird, the horned lark, which can experience daily temperature fluctuations up to 30 °C (Camfield and Martin 2009) and nest predation rates that vary by up to 250% across years (MacDonald et al. 2016). Females incubate without matefeeding (Beason 1995), strengthening the potential relationship between maternal condition and offspring development. ...
Thesis
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Offspring development is a critical life-history stage for altricial songbirds and a prime target for selection, as predation risk is high relative to other life-stages and environmental conditions can induce lasting consequences for life-time fitness. Nestling development rates vary widely among species, populations, and individuals. Rapid development is considered an evolved response to improve nest success given high predation risk at the species or population level. However, it is unclear what drives variation in development rate among individuals and whether offspring or parents have the adaptive capacity to respond to prevailing stressors. I investigated the relative influence of multiple, interacting drivers from across the annual cycle on offspring developmental variation within an alpine breeding population of horned lark (Eremophila alpestris) by integrating ecological observations, behavioural experiments, physiology, and light-level geolocators to track migration. I demonstrated that rapid development was associated with a greater probability of nest success, confirming a selective advantage to fledging quickly. Cold ambient temperatures during the nestling period prolonged development, potentially due to resource constraints or thermoregulatory challenges, but females in better body condition were able to buffer offspring against harsh, early season conditions, enabling rapid development. With elevated predation risk, nestlings left the nest earlier by increasing wing growth. This effect was mediated by predator-specific glucocorticoid responses (stress biomarker) and parental provisioning behaviour. During spring migration, I showed that 59% of adults conducted extended stopovers (mean = 41 days) and subsequently had greater reproductive success during the breeding season. However, periods of extreme cold during stopover were correlated with prolonged offspring development, resulting in a lower probability of nest success. My results demonstrate that: 1) nestlings have the adaptive ability to respond to elevated predation risk, 2) parental care can mediate offspring development in response to suboptimal conditions, and 3) prolonged stopovers may be key components of the annual cycle for alpine larks. By addressing within-population variation, I offer new insights into the eco-evolutionary drivers that shape offspring development across the annual cycle with implications for individual fitness and, ultimately, population-level responses to rapidly changing environments.
... As part of a long-term monitoring project of an alpine-breeding population of Horned Larks (Eremophila alpestris) in northern British Columbia, Canada (Camfield et al. 2010), 162 unbanded adults were captured using bownets from 2003 to 2015. During the 2016 and 2017 field seasons, we needed to recapture previously banded individuals to remove light-level geolocators, but encountered avoidance of bownet traps. ...
... 89,No. 4 approximately the 11th day of incubation when nests began to be visited daily to accurately record hatch date (12-d average incubation; Camfield and Martin 2009). We deployed both trap types 5-8 d post-hatching when parental provisioning rates of nestlings is high and the likelihood of causing premature fledging is low. ...
Article
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Capturing nesting songbirds is a core component of many field studies. However, avoidance of traps and mist‐nets by birds can reduce capture efficiency and bias study results, particularly when individuals need to be recaptured multiple times. We describe a novel capture method—the noose‐line—for an alpine population of Horned Larks (Eremophila alpestris) studied during three breeding seasons (2015–2017) in northern British Columbia, Canada. Our objective was to develop a safe, efficient method to recapture individuals that exhibited trap avoidance. We compared the capture efficiency (trap success relative to capture effort) and fitness consequences (nest survival and nest attentiveness) of the noose‐line (non‐selective method) to those of a more traditional bownet trap (selective method) for both naïve (not previously captured) and previously captured Horned Larks. Mean trapping success for the noose‐line was high for both naïve (89.7%) and previously captured (62.9%) birds, whereas mean trapping success for the more visible bownet was strongly influenced by bird experience (naïve = 41.4%, previously captured = 12.1%). However, mean capture effort (time required for successful capture) was greater for noose‐lines than the bownet (45.3 min vs. 17.5 min) and noose‐lines were more likely to capture non‐targeted individuals. The trap type used to capture birds did not influence nest survival. Overall, our results suggest that noose‐lines can be an effective option for capturing ground‐nesting songbirds, particularly for studies where birds must be recaptured, e.g., to retrieve tracking devices or repeatedly measure body condition.
... Under normal temperature fluctuations, incubating adults often engage in subtle behavioral adjustments to achieve a balance between the parents' physiological demands and maintaining developmental temperatures for embryos. For example, avian species have been found to shorten nest off-bout duration (Coe et al., 2015) and increase nest attentiveness (Camfield and Martin, 2009) during challenging environmental conditions. Because incubation behavior of adults and the microclimate of developing offspring are closely linked (Martin et al., 2007;Coe et al., 2015), these behavioral adjustments likely correspond to maintaining optimal developmental incubation temperatures. ...
... Additionally, the weather effects of average ambient temperature and daily precipitation strongly influenced the incubation behavior of total number of daily off-bouts. Furthermore, unlike previous studies that found ambient temperature strongly influenced nest attentiveness (Kovařík et al., 2009;Camfield and Martin, 2009), we found no relationship in our results for bobwhite, but scaled quail nest attentiveness was influenced. This suggests that while weather influences the duration and frequency of bouts, ground-nesting species, particularly bobwhite, may be not be flexible enough in their physiology and behavior to incubate developing embryos consistently during periods of suboptimal conditions. ...
Article
Behavioral adjustments and parental decisions during reproduction can influence the thermal environment at nests, yet our understanding into how environmental factors (i.e., temperature and precipitation) constrain an adult's ability to balance self-maintenance and incubation demands is limited. To expand our understanding of how species respond to environmental factors, we investigated the reproductive ecology of two ground-nesting species (northern bobwhite [Colinus virginianus] and scaled quail [Callipepla squamata]) in a region (i.e., the Southern Great Plains) prone to thermal variability (i.e., extreme hot and cold temperatures). Specifically, our objective was to examine how temperature and precipitation directly influenced behavioral adjustments (i.e., off-bout duration, frequency, and nest attentiveness) and parental decisions (i.e., nest site selection), and indirectly influenced nest fate. Overall, we found that parents chose to nest in sites that were significantly cooler in temperature than randomly selected sites, and parents further altered the thermal environment experienced by embryos through incubation behavior. Daily precipitation and average ambient temperature and/or their interaction best predicted incubation behaviors, yet each species differed in the timing (i.e., morning vs. evening), frequency, and duration of off-bouts. Furthermore, successful nests were associated with cooler nest site temperatures for bobwhite and warmer nest site temperatures for scaled quail. Our finding of relatively stable (35.5 °C) incubation temperature for developing embryos of both species suggests that ground-nesting birds are able to regulate microclimate through behavioral adjustments and parental decisions even under extreme temperature fluctuations. Nevertheless, the ability for a ground-nesting species to effectively modify behavioral adjustments and decisions may be altered during long periods of enhanced physiological and environmental stress.
... We collected data on nest characteristics for an alpine population near Smithers, British Columbia, Canada (54.8°N, 127.3°W), during the 2015 and 2016 breeding seasons. All nests were located within a 4-km 2 study site above the tree line in alpine tundra (1650-2000 m asl), characterized by high winds, fluctuating daily temperatures and snow cover extending into June (Camfield & Martin 2009). Ambient temperatures measured at~3 m above ground level varied between years, as early season daily temperatures (May to mid-June) were on average 6.4°C in 2015 compared with 2.7°C in 2016, with temperatures on 3 and 18 days averaging below freezing, respectively. ...
... Although nestling size traits were comparable among substrates, nests in heather had lower hatching success. A cooler intrinsic microclimate in heather substrate may even provide a refuge from late-summer heat when daytime highs can reach over 40°C for several hours at ground level and potentially cause heat stress for nestlings (Camfield & Martin 2009). Once ambient conditions are warm, predation risk may influence substrate choice. ...
... Incubation behavior may provide a more explicit care variable than feeding behaviors (Harrison et al. 2009). The high energy demands of incubation may be extraordinarily challenging for birds breeding in alpine environments with typically low and extensively fluctuating ambient temperatures (Camfield and Martin 2009). The need for cooperation, as well as the extent of parental conflict, is accentuated in harsh environmental conditions (Kosztolányi et al. 2006). ...
... This supports Jones et al.'s (2002) hypothesis that individuals should maximize the success of the present breeding attempt while making sure the cost to their future reproductive potential is minimized, thus enhancing their lifetime reproductive success, because a small decrease in parental effort will lead to a high risk of failure under harsh ecological situations. A study on Horned Larks (Eremophila alpestris) in an alpine environment also reported that parents may compensate for the shorter breeding season and decreased re-nesting chances by enhancing parental care (Camfield and Martin 2009). ...
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The biparental incubation model is an excellent one for investigating how parents resolve sexual conflict and achieve cooperation, especially in cold alpine environments. We used video monitoring of 20 nests 24 h/day to systematically investigate the incubation pattern of the Black-necked Crane (Grus nigricollis), a biparental waterbird with threatened status (International Union for Conservation of Nature vulnerable status), inhabiting the Qinghai-Tibetan Plateau, China. Analysis of 3886 h of video recordings indicated high nest attendance (90.1%) by Black-necked Crane parents across 14 nests, with almost equal female and male nest attendance (45.4 vs. 44.8%). The average length of an incubation bout was 2.06 h, with frequent changeovers (10.87 times/day, lasting on average 5.05 min). Males spent significantly more time returning to the nest than females (5.57 vs. 4.65 min, t180 = −46.61, P < 0.001) after the partner left the nest. Six of 20 monitored nests failed, mainly due to egg predation, egg collection, or adverse weather. We provide the first evidence that, under natural environmental conditions, both males and females respond to reduced partner effort with diverse strategies. On average, full compensation was greater than 100% for the decreased partner effort. In this long-lived species with long-lasting pair bonds and low fecundity, a mate may overly compensate for reduced partner investment to avoid forfeiting the current breeding attempt. Our results indicate that females and males are allocated different tasks with complementary patterns during incubation, enhancing egg care efficiency in an alpine plateau environment with severe threats. Both social and natural environmental factors may shape the incubation pattern of Black-necked Cranes.
... Along with predation pressure, food availability, clutch size, and female age and condition, variation in weather may cause incubating parents to adjust the duration of on-and off -bouts in order to maintain a relatively stable thermal environment (Yerkes 1998, Deeming 2002, Hepp and Kennamer 2011. For example, a few studies have shown that higher ambient temperatures can be associated with reduced incubation period (Ardia et al. 2006), increased off -bout duration (Conway and Martin 2000, Camfi eld and Martin 2009, Boulton et al. 2010, and greater on-and off -bout egg temperatures relative to cooler ambient temperatures (Ardia et al. 2009). In some species, precipitation has also been shown to play a role in determining female incubation behavior through increasing off -bout duration (Skrade and Dinsmore 2012). ...
... Tree swallows are a widely studied passerine bird, yet a detailed description of their incubation behavior in relation to egg temperatures is lacking. Based on previous studies (Conway and Martin 2000, Ardia et al. 2006, Camfi eld and Martin 2009, Boulton et al. 2010, Skrade and Dinsmore 2012, we predicted that ambient temperature and rainfall, individually and/or interactively, would infl uence female incubation behavior through diff erences in number of off -bouts, duration of off -bouts, and incubation constancy (total time spent incubating divided by the total time of the active period; 06:30 -20:00). Furthermore, we predicted that female behavior would be associated with changes in incubation temperature such that at a given ambient temperature, increased incubation constancy would increase egg temperature and decrease egg temperature variation. ...
Article
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Incubation is an important component of avian parental care and slight changes in incubation temperature can affect offspring phenotype. Although many extrinsic and intrinsic factors may generate variation in incubation temperature, they remain underexplored under natural conditions. Using a robust data set encompassing 55 nests, 22 816 behavioral observations, and > 1 million paired ambient and egg temperatures, we describe the relationships among abiotic factors, female incubation behavior, incubation temperature, and incubation period for tree swallows Tachycineta bicolor. We report a large amount of individual variation in incubation behaviors and average incubation temperatures for our study population. The average on-bout incubation temperature was 34.1°C, with daily egg temperatures ranging from 18.0–39.2°C. Females modulated the number of times they left the nest and the amount of time they stayed off the nest according to interactions between precipitation and temperature patterns. Models generated from our observations predicted that the number of female off-bouts was the lowest under warm and dry conditions while more off-bouts were taken under cold and dry or warm and wet conditions. During cold and dry conditions, females stayed off their nest ∼4 times longer than under warm and dry conditions. However, this pattern was reversed under periods of rainfall; females tended to take shorter off-bouts when it was rainy and cold compared to longer off-bouts during warmer rain events. Furthermore, variation in female behavior was associated with differences in overall incubation temperature such that females that maintained greater incubation constancy produced higher incubation temperatures at a given ambient temperature than those that displayed lower incubation constancy. Our results provide perspective on the timing of breeding, as some of the advantages of breeding early may be countered by cooler, early season temperatures and precipitation that cause reproducing females to favor self-maintenance at a potential cost to optimal incubation temperatures for offspring development.
... General adjustments to the variables in the cost-benefit analysis, such as age, sex, remaining proportion of the incubation period and potentially harmful ambient temperatures, will be included in the behavioural norm (e.g. Biermann and Robertson 1981;Camfield and Martin 2009). ...
... The reduction of FID over time may be caused by the need to protect the eggs from dangerous cooling when ambient temperatures drop during evening hours (Camfield and Martin 2009). Alternative explanations of the observed time effect are (a) the sexes switched incubation duties during the evening (c.f. ...
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Flight initiation distances (FIDs) of nesting birds approached by a predator likely reflect evolutionary stable strategies in which birds make trade-offs between adult survival and reproductive success. Here, we test if FID (a) had an impact on hatching success, (b) was adjusted to current conditions, and (c) was consistent for individual nests. All experiments were performed with a human approaching incubating Eurasian curlews Numenius arquata, a ground-nesting wader species under high egg predation pressure. Our results show that hatching success was higher in nests where the incubating parent left at intermediate FIDs compared to short and long ones, and that FID decreased with date and time of the evening. Further, FIDs from repeated approaches were not consistent within nests. We suggest that incubating Eurasian curlews follow a “surprise” strategy, where an element of randomness is superimposed on a context-adjusted norm to prevent predators from predicting their FID behaviour.
... Topographic characteristics such as elevation, slope, and aspect often influence the microhabitat and the microclimate of a nest and hence can influence incubation behaviour and breeding success in high-Alpine bird species (Camfield and Martin 2009;MacDonald et al. 2016;Niffenegger et al. 2023a, b). Habitat structures in the surroundings of the nest, including perches and shelter for the fledglings, can also explain nest site selection. ...
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Birds breeding in high-Alpine habitats must select a suitable breeding site and achieve successful reproduction within a restricted time. During four breeding seasons, we monitored nest sites of the Northern Wheatear ( Oenanthe oenanthe ), a high-Alpine long-distance migrant. We investigated how ecological factors predicted the selection of a site for nesting within the home range, using conditional logistic regression. Birds preferred south-exposed productive pastures on gentle slopes, interspersed with non-vegetated ground and human-made rockpiles. The direct vicinity of conspecific nests was avoided, as were shrubby or north-exposed areas. We investigated if habitat also influenced breeding success. We analysed the impact of environmental factors on breeding success, which was primarily driven by predation. The probability of the brood fledging successfully decreased on north-exposed slopes or on areas with low coverage of non-vegetated ground. The vicinity of conspecific nests did not have a clear effect. Further, we describe how breeding success varied within and between years. Within years, replacement broods had a higher breeding success. The apparent absence of variation in breeding success between years and a delay of the breeding period in the year with late spring onset suggest a high level of tolerance with respect to inter-annual variation of meteorological conditions. Since the preferred habitat is still widely available in the Alps and given the negative population trends in Western Europe, the Alpine range might serve as a refuge for the Northern Wheatear, as long as low-intensity management and heterogenous habitats are maintained.
... Incubation intensity largely determines the early developmental trajectory of bird embryos (DuRant et al. 2013). Ectothermic bird embryos need an optimal developmental temperature (36-38°C; Tieleman et al. 2004), which is not often matched by the environment (Camfield & Martin 2009). This challenge for birds is accentuated when only one parent incubates (Hu et al. 2024). ...
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The negative impact of environmental pollution on avian physiology and breeding success is well documented. However, pollution-related behavioral changes during reproduction remain underexplored, despite behavior often being one of the earliest indicators of environmental disturbances and having significant life-history consequences. For example, altered food availability in a polluted environment could potentially perturb the incubation behavior of income breeders. These birds typically alternate between staying in the nest and heating eggs (on-bout) and taking foraging trips (off-bout). In this two-year study (2020 and 2022), we investigated how the incubation behavior of an insectivorous passerine, the pied flycatcher (Ficedula hypoleuca), varied with environmental pollution levels around a Cu-Ni smelter. Additionally, we compared two different metrics – temperature and humidity within the nest – to evaluate their use as indicators of incubation rhythm. We found that temperature- and humidity-based incubation rhythm parameters correlated, but those based on humidity matched better the true incubation behavior documented by simultaneous video recording. This was because the humidity curve showed a more immediate and intensive response to the female's incubation behavior. Birds in the polluted area took slightly more (11%) but shorter (11%) off-bouts, possibly reflecting smaller energetic constraints or better food availability in the polluted area. However, we found no difference in total incubation intensity between polluted and control areas, with F. hypoleuca females incubating their eggs 75% of the daytime in both environments. Hence, incubating females in the polluted area did not allocate more time for gathering their energy reserves than the birds in the control area, and there was also no difference in the hatching success. Our study is the first to use humidity variation to record incubation rhythm, and our results indicate that measuring humidity inside the nest is a promising technique to test and develop further. For example, further studies are needed to test if this method would work in different types of nests. From an environmental protection standpoint, our results also contribute valuable insights to the relatively limited information on pollution-related behavioral changes.
... Reproduction requires an important investment of time and energy, and breeding individuals must strike a balance between survival and reproduction during this critical period. In birds, incubation can be one of the most energetically demanding stages of reproduction [1,2], especially in extreme environments [3]. Harsh and unpredictable Arctic environments can for instance induce a high pressure on reproductive individuals. ...
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Complex incubation strategies have evolved to solve the trade-off between parent survival and care for their eggs with often brief departures (recesses) that maximize egg survival, and infrequent extended recesses maximizing adult condition. Here we examined incubation behaviour of sanderlings (Calidris alba), a species that exhibits both biparental and uniparental incubation behaviour. During 11 breeding seasons in Greenland, we have quantified incubation variability with thermologgers placed in nests. We estimated the impact of environmental conditions and individual characteristics on the occurrence and the duration of recesses. We found that extended recesses are a unique feature of uniparentals, and their frequency and duration increased in colder temperatures. The relationship was mediated by body condition, with individuals in poor condition performing longer extended recesses in colder temperatures. This suggests that extended recesses may represent a shift towards self-maintenance at the expense of the egg care, allowing birds to continue incubating under unfavourable conditions. Our study illustrates how extended recesses may be a key breeding strategy to overcome high energetic costs associated with incubation. Quantifying such behavioural flexibility paves the way for tracking future behavioural responses of individuals in the face of changing environments.
... Nesting ecology is particularly interesting for birds in ecosystems defined by cold climates, such as the alpine and tundra biomes. In these extreme seasonal systems, breeding periods are restricted to a narrow temporal window and there are limited opportunities for second breeding attempts (Camfield and Martin 2009). Individuals must cope with a variety of environmental factors (Martin and Wiebe 2004), including limited nesting potential in years with high snowfall that lingers on mountain peaks (Clarke andJohnson 1992, Frederick andGutiérrez 1992) and inclement weather (Novoa et al. 2008, Martin et al. 2017. ...
... Parent behaviour at the nest suggested sensitivity to increases in temperature. Incubation bout duration and provisioning rates were highest early in the morning and late afternoon, likely an avoidance of temperature extremes to minimise cooling and rewarming costs (Tieleman et al. 2004;Martin and Camfield 2009). On hot days, female birds were regularly observed shading both nestlings and eggs while panting. ...
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The Agulhas Long-billed Lark Certhilauda brevirostris is restricted to the Agulhas Plain, South Africa, a region extensively transformed for crop production and sheep grazing. We present data on nest and egg characteristics, clutch and brood size, parental care and breeding success previously undescribed for this species. During field surveys in 2020 and 2021, 29 nests were located. Of these, 16 were monitored by camera traps. Laying started in late winter (July) and continued until early summer (late November). Most nests (66%) were in Renosterveld, a unique vegetation component of the Fynbos Biome, with the remainder in human-modified landscapes. Female larks were responsible for nest construction and incubation. Both sexes provisioned nestlings, with provisioning rate related to nestling age and time of day but not brood size. Breeding success was low, with only 14% of nests fledging any young. Only one repeat nesting attempt following a predation event was observed, but the attempt was abandoned. Nest predation was the main cause of nest failure, with eight species of nest predators identified. An apparent preference for nesting in Renosterveld highlights the need for protection of this endangered habitat type. As a ground-nesting species in an agriculturally transformed landscape, this lark faces numerous threats associated with habitat loss, altered predation pressure, exposure to pesticides and disturbance at nest sites.
... For 12 years (2003-2007, 2010-2011 and 2015-2019), we studied a breeding population in ~3 km 2 of alpine tundra (1,650-2,000 m a.s.l.) in northern British Columbia (54.8°N, 127.3°W). Breeding conditions are challenging, with high wind speeds, daily temperatures that fluctuate from −5 to +35°C, and snow cover often extending into June (Camfield & Martin, 2009;Martin et al., 2017). Breeding pairs initiate one to two nests per season with an average of 3.6 eggs (range: 2-5; Camfield et al., 2010). ...
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In seasonal environments, fluctuating early‐season weather conditions and short breeding windows limit reproductive opportunities such that breeding earlier or later than the optimum may be particularly costly. Given the risk of early‐season energy limitations, time‐ and energy‐based carry‐over effects stemming from environmental conditions across the annual cycle may have pronounced consequences for breeding phenology and fitness. Generally, when and where environmental conditions are most influential are poorly understood, limiting our ability to predict the future of climate‐sensitive populations. For an alpine‐breeding, migratory population of horned lark Eremophila alpestris in northern British Columbia, Canada (54.8°N), we assessed how weather conditions across the annual cycle influenced clutch initiation date and offspring development. We also addressed how cross‐seasonal effects on breeding parameters combine to influence reproductive fitness. With 12 years of breeding data and 3 years of migration data, we used a sliding window approach to identify points during the annual cycle when weather events most influenced breeding phenology and offspring development. Consequences for breeding success were assessed using nest survival simulations. Average clutch initiation date varied up to 11 days among years but did not advance from 2003 to 2019. Warmer temperatures at stopover and breeding sites advanced clutch initiation, but winter conditions had no effect. Sub‐zero stopover temperatures carried over to prolong offspring development independent of clutch initiation date, potentially indicating energy‐based carry‐over effects acting on parental investment. Nest survival decreased with both later clutch initiation and prolonged offspring development such that females nesting earlier and fledging offspring at a younger age were up to 45% more likely to reproduce successfully. We demonstrate that stronger carry‐over effects originated from environmental conditions closer to the breeding site in time and space, as well as the potential for energy‐based mechanisms to link pre‐breeding conditions to reproductive fitness. We also highlight the importance of extended stopovers for songbirds breeding in seasonal environments, particularly given that climatic conditions are becoming increasingly decoupled across stages of the annual cycle. Understanding the cross‐seasonal mechanisms shaping breeding decisions in stochastic environments allows for more accurate predictions of population‐level responses to climate change.
... Several studies examined the relationship between ambient temperature and incubation behaviour in birds, and the one frequent finding is that the lower temperatures caused females to spend less time off the nest per bout (Conway and Martin, 2000a, b;Ardia et al. 2010;Boulton et al. 2010;Amininasab et al. 2016). Moreover, a few studies have shown that higher ambient temperatures can be associated with reduced incubation period (Ardia et al. 2006) and increased off-bout duration (Conway and Martin 2000a, b;Camfield and Martin 2009;Boulton et al. 2010). In contrast, Pérez et al. (2008) experimentally heated eggs of the tree swallow (Tachycineta bicolor) during incubation by an average of 6.9 °C and showed that in boxes with elevated temperature females increased time spent in the nest during incubation. ...
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Ambient temperature experienced by an animal during development or subsequently as an adult can affect many aspects of its behaviour and life-history traits. In birds, egg incubation is a vital component of reproduction and parental care. Several studies have suggested that environmental factors (such as nest microclimate) can influence the ability of incubating parents to maintain suitable conditions for embryo development. Here, we manipulated the developmental conditions of embryos through a modification of nest box thermal microclimate to investigate female incubation behaviour and its impact on offspring fitness-related traits in a wild population of the Collared Flycatcher ( Ficedula albicollis ). The temperature in experimental nests was increased using a heat-pack placed under the roof of a nest box, resulting in an average temperature increase of 2.5 ºC, which corresponds to projected climate change scenarios. We demonstrated that females from nests with elevated temperature spent less time in the nest box during egg incubation and had more off-bouts than females from control nests. Moreover, we found that offspring from the experimentally heated nests had larger body mass at fledging in comparison to the control ones. Our study indicates that nest microclimate during the incubation period affects female incubation behaviour and offspring quality, indicating that environmental variation in nest temperature early in ontogeny can have important and long-lasting fitness consequences.
... This trait may be correlated with open-cup nesting and colder environments. To escape predators or inclement weather, rapid growth and physiological development is crucial for the survival of open-cup altricial nestlings (Camfield and Martin 2009;Coslovsky and Richner 2011;Cheng and Martin 2012). This concept is supported by our thyroid hormone results which demonstrate rapid thermogenesis development in Asian Short-toed Lark nestlings enabling them to leave the nest as young as 8 days old. ...
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Background In high latitude grassland habitats, altricial nestlings hatching in open-cup nests early in the breeding season must cope with cold temperature challenges. Thyroid hormones (triiodothyronine, T 3 and thyroxine, T 4 ) and corticosterone play a crucial role in avian thermoregulation response to cold. Investigating the endocrine response of altricial nestlings to temperature variation is important for understanding the adaptive mechanisms of individual variation in the timing of breeding in birds. Methods We compared nest temperature, ambient temperature, body temperature, plasma T 3 , T 4 and corticosterone levels in Asian Short-toed Lark ( Alaudala cheleensis ) nestlings hatching in the early-, middle-, and late-stages of the breeding season in Hulunbuir grassland, northeast China. Results Mean nest temperature in the early-, middle- and late-stage groups was − 1.85, 3.81 and 10.23 °C, respectively, for the 3-day-old nestlings, and 6.83, 10.41 and 11.81 °C, respectively, for the 6-day-old nestlings. The nest temperature significantly correlated with body temperature, plasma T 3 , T 4 and corticosterone concentrations of nestlings. Body temperature of 3-day-old nestlings in the early and middle groups was significantly lower than that of the late group, but there was no significant difference between the nestlings in the early and middle groups. The T 4 and T 3 concentrations and the ratio of T 3 /T 4 of both 3- and 6-day-old nestlings in the early-stage group were significantly higher compared to the middle and late groups. The corticosterone levels of 3-day-old nestlings were significantly higher in the early-stage group compared to the middle- and late-stage groups. Conclusion Nestlings hatching early responded to cold temperature by increasing thyroid hormones and corticosterone levels even in the early days of post hatching development when the endothermy has not been established. These hormones may play a physiological role in neonatal nestlings coping with cold temperature challenges.
... Environmental shifts can alter avian migratory and reproductive phenology, especially in the Arctic which offers a short favorable window for those breeding, notably via spatio-temporal constraints in prey availability at extreme latitudes (Martin and Wiebe, 2004). Higher air temperatures have been shown to directly impact reproduction by advancing lay dates, accelerating embryonic growth, and decreasing incubation attentiveness in birds (Camfield and Martin, 2009;Visser et al., 2009;Durant et al., 2010;Nord and Nilsson, 2011). Lowered incubation attentiveness can not only extend the incubation period and potentially impact successful hatching and fledging through heightened predation risk (Conway and Martin, 2000;Smith et al., 2012;Higgott et al., 2020), but it can also leave the female in worse body condition relative to females with lower incubation effort through increased time spent maintaining optimal clutch temperature (Bottitta et al., 2003;D'Alba et al., 2009;Høyvik Hilde et al., 2016). ...
Article
Wildlife are exposed to multiple stressors across life history stages, the effects of which can be amplified as human activity surges globally. In Arctic regions, increasing air and ocean temperatures, more severe weather systems, and exposure to environmental contaminants all represent stressors occurring simultaneously. While Arctic vertebrates, including marine birds, are expected to be at risk of adverse effects from these individual stressors, few studies have researched their combined impacts on breeding behaviour and reproductive success. The interactive effects of environmental conditions and mercury (Hg) contamination on laying phenology and incubation behaviour were examined in female common eiders (Somateria mollissima, Mitiq) nesting at Canada's largest Arctic breeding colony. Exposure to higher pre-breeding air temperatures were linked to females with higher egg Hg concentrations laying earlier than those with lower Hg values. Furthermore, examination of a total of 190 days of incubation behaviour from 61 eiders across two years revealed a negative relationship between wind speed and the frequency of incubation interruptions. Importantly, exposure to higher air temperatures combined with lower Hg concentrations was significantly correlated with increased incubation interruptions. Although previous research has shown that warmer spring temperatures could afford lower quality females more time to improve body condition to successfully lay, results suggest these females may face stronger cumulative fitness costs during incubation in warmer years, potentially in combination with the effects of Hg on physiological stress and hormone secretion. This study highlights how multiple stressors exposure, driven by human-induced environmental changes, can have a complex influence on reproduction.
... Females have also been reported to increase diurnal nest attentiveness as the breeding season progresses (Ardia et al. 2009), which would compensate for shorter nocturnal incubation periods as daylight lengthens throughout the spring (Bueno-Enciso et al. 2017). We found however that females shortened on-bouts, decreasing nest attentiveness along the season (Camfield and Martin 2009). It should be noted that this effect appeared even though our analyses were restricted to first clutches, with a range for the onset of incubation of 7-21 days depending on year and population, so the variation in daylength was relatively small. ...
Article
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Avian embryos need a stable thermal environment to develop optimally, while incubating females need to allocate time to self‐maintenance off the nest. In species with female‐only incubation, eggs are exposed to ambient temperatures that usually cool them down during female absences. The lower the ambient temperature the sooner females should return to re‐warm the eggs. When incubation constraints ease at increasing ambient temperatures, females respond by increasing either incubation effort or self‐maintenance time. These responses are population‐dependent even within the same species; but it is uncertain whether they are caused by local environmental conditions or they are an artefact from limited datasets, different methodological approaches or the timescale over which incubation behaviour is measured. In this study, we collected incubation data from three Mediterranean great tit Parus major populations during three consecutive years. We measured the duration of each off‐ and on‐bout event, used these variables to compute nest attentiveness at three different timescales (full incubation, daily and hourly periods) and assessed the impact of ambient temperature on bout duration and nest attentiveness. We found that females maximized on‐bout duration at different local temperatures, ranging from 10 to 20°C; but lengthened off‐bouts linearly across a range of 0–38°C in all three populations. These local differences translated into opposite linear nest attentiveness patterns at the full incubation scale: Females increased either incubation effort, longest on‐bouts between 15 and 20°C or self‐maintenance time, longest on‐bouts at 10°C. It was at daily and hourly periods when we detected non‐linear nest attentiveness patterns, as expected from on‐bout duration, peaking at different local ambient temperatures. Females first increased incubation effort up to a certain temperature value and then increased self‐maintenance time at the highest ambient temperatures. Further research is needed to understand which factors are behind the turning points from one behaviour to the other.
... Our urban site had an average of 2.3 • C higher temperatures than our rural site ( Figure 1D). The majority of studies have reported that incubating adults respond to elevated temperatures by decreasing incubation effort due to reduced thermostatic demand (Kendeigh, 1952;Haftorn, 1979;Conway and Martin, 2000a,b;Londoño et al., 2008;Camfield and Martin, 2009;Álvarez and Barba, 2014;Amininasab et al., 2016). For example, urban pale breasted thrush (Turdus leucomelas) that built their nests on buildings decreased nest attentiveness as compared to ones that built nests on trees because buildings increase nest temperatures (Batisteli et al., 2020). ...
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As global land surfaces are being converted to urban areas at an alarming rate, understanding how individuals respond to urbanization is a key focus for behavioral ecology. As a critical component of avian parental care, incubating adults face a tradeoff between maintaining an optimal thermal environment for the developing embryos while meeting their own energetic demands. Urban habitats are biotically and abiotically different from their rural counterparts, i.e., in food availability, predator compositions, and the thermal environment. Therefore, urban birds may face different incubation challenges than their natural counterparts. We measured incubation behavior of rural and urban house wrens, Troglodytes aedon, with temperature loggers throughout the 12-day period. We found that urban females had more incubation bouts of shorter duration and spent less total time incubating per day than rural females. Results could provide evidence of behavioral shifts of wrens in cities, which have implications for the evolution of parental care. Our findings contribute to our understanding of the behavioral traits needed for city life and possible environmental pressures driving urban adaptations.
... Incubation is a fundamental element of avian parental behavior, and it requires an essential investment in caring for offspring by the incubators (Camfield and Martin, 2009;Bulla et al., 2015). This care requires a great deal of time and energy from both parents, increasing the fatality rate of parents or reducing the size of future generations (Clutton-Brock, 1991;Székely et al., 2006;McGraw et al., 2010;Nord and Williams 2015;Williams, 2018). ...
Article
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Saunders’s terns (Sternula saundersi) are a small, ground-nesting marine bird species that have a massive rearing range, including the shores and islands of Asia and Africa adjacent to the north Indian Ocean. Despite occupying a large breeding range, little is known about the breeding ecology of this species. This research explored aspects of Saunders’s terns’ breeding ecology and predation rate in 2013 on the Farasan Islands of Saudi Arabia. The outcomes confirm that the mean clutch size of a Saunders’s tern was 1.77 ± 0.08 (n = 31) eggs per clutch and the mean egg size was 31.05 x 23.15 mm. The results of this study show a remarkable relationship between clutch size and egg volume and length (p = .002, p = .004, respectively). Predation was the major reason for nest damage (62.5%). Evidence from cameras at nests showed that the predators of Saunders’s tern nests on the Farasan Islands were white-tailed mongoose (Ichneumia albicauda) and Egyptian vultures (Neophron percnopterus). This is the first study on the breeding ecology of Saunders’s terns, and it shows that predator control is essential to the existence of the species. The results of this study suggest that fencing some breeding sites may help to minimize human disturbance and decrease the risk of nest predation from mammalian predators. Further research is needed to compare the predation rates on the mainland and islands and to develop efficient strategies to conserve this ground-nesting species.
... There is evidence that microclimate can be important in influencing habitat selection in mountain birds which may explain our findings. For example, it has been shown that Horned Larks Eremophila alpestris adjusted the amount of incubation time in response to microclimatic conditions (Camfield and Martin 2009) by spending less time on the nest as temperatures in the nest surrounding increased, which may imply energy savings in warmer microclimates. Furthermore, microclimate and aspect strongly influenced nestling survival in Water Pipits (Rauter et al. 2002). ...
Article
Predictions derived from species distribution models (SDMs) are strongly influenced by the spatial scale at which species and environmental data (e.g. climate) are gathered. SDMs of mountain birds usually build on large-scale temperature estimates. However, the topographic complexity of mountain areas could create microclimatic refuges which may alter species distributions at small spatial scales. To assess whether fine-scale data (temperature and/or topography) improve model performance when predicting species occurrence, we collected data on presence–absence of bird species, habitat and fine-scale temperature at survey points along an elevational gradient in the Alps (NW Italy). Large-scale temperature data, and both large- and fine-scale topography data, were extracted from online databases for each point. We compared species models (fine-scale vs large-scale) using an information-theoretic approach. Models including fine-scale temperature estimates performed better than corresponding large-scale models for all open habitat species, whereas most forest/ecotone species showed no difference between the two scales. Grassland birds such as Northern Wheatear Oenanthe oenanthe and Water Pipit Anthus spinoletta were positively associated with warmer microclimates. These results suggest that alpine grassland species are potentially more resistant to the impact of climate change than previously predicted, but that indirect effects of climate change such as habitat shifts (forest- and shrub encroachment at high elevations) pose a major threat. Therefore, active management of alpine grassland is needed to maintain open areas and to prevent potential habitat loss and fragmentation. SDMs based solely on large-scale temperatures for open habitat species in the Alps should be re-assessed.
... Further, extrinsic factors, such as ambient temperature, and intrinsic factors, such as the physical condition of the incubating parent, can influence incubation behavior and temperature. For example, ambient environmental temperatures can have a positive relationship with incubation temperature (Camfield and Martin 2009, McClintock et al. 2014, Coe et al. 2015, Amininasab et al. 2016; but see Conway and Martin 2000) and can have either a negative (Afton 1980, Webb and King 1983, Afton and Paulus 1992, Norment 1995, Boulton et al. 2010, MacDonald et al. 2014, Coe et al. 2015, Klimczuk et al. 2015 or positive (Morton andPereyra 1985, Zuberogoitia et al. 2018) relationship with the amount of time that a parent spends incubating. Additionally, body mass is related to the amount of time spent incubating, with parents of lower body mass spending less time incubating than heavier parents (Afton and Paulus 1992, Criscuolo et al. 2002, Hanssen et al. 2002, Gorman and Nager 2003, Cresswell et al. 2004, Ardia and Clotfelter 2007, Tombre et al. 2012. ...
Article
For many animals, parental care behavior is an important aspect of their life history that affects both parents and offspring. In birds, one of the most important parental care behaviors is incubation, which is costly to the parent but directly influences embryonic development and fitness of offspring. Some birds exhibit the intriguing behavior of partially incubating their eggs prior to clutch completion for only a portion of each day. This partial incubation is characterized by lower incubation temperatures and constancy than during full‐time incubation, which typically begins at clutch completion. Partial incubation may preserve the viability of eggs laid early in the laying sequence, shorten the length of the full incubation period, and/or provide a favorable microclimate to the incubating parent. It might also reduce the probability of nest predation, nest site takeover by another bird, brood parasitism, and/or predation of the adult. Although there is evidence that partial incubation is an adaptive behavior and that time invested in this behavior varies among individuals of the same species, nothing is known about what may drive this inter‐individual variation. To investigate how environmental and parental characteristics may be related to partial incubation behavior, we studied the partial incubation behavior of wood ducks (Aix sponsa) using artificial egg temperature loggers within nest boxes. Our results suggest that females with greater mass relative to their structural size invest more time in partial incubation. Additionally, the incubation temperature and length of on‐bouts of partial incubation increased over the course of the partial incubation period, and ambient temperature during on‐bouts was positively related to incubation temperature. Ultimately, our study suggests that characteristics of both the environment and parent may influence the partial incubation behavior of wood ducks, and improves our understanding of an important, but understudied, aspect of avian parental care. This article is protected by copyright. All rights reserved.
... The extreme environmental conditions these species are experiencing may strongly affect foraging behav-iour, as they may severely affect prey availability and/or the costs of transportation. This is especially the case during reproduction, when parents may be forced to carefully allocate resources to self-maintenance vs. parental care, and foraging decisions may therefore have potentially important consequences for fitness (Martin & Wiebe 2004, Camfield and Martin 2009, Liang et al. 2018. ...
Article
During breeding, parents of avian species must increase their foraging efforts to collect food for their offspring, besides themselves. Foraging trips are thus a key aspect of the foraging ecology of central-place foragers when rearing their offspring. However, studies of the foraging ecology of high-elevation specialists inhabiting harsh environments are scarce. Here we report for the first time quantitative information on ecological determinants of foraging trips in the White-winged Snowfinch (Montifringilla nivalis), a high-elevation specialist threatened by climate warming. We focused on seasonal, meteorological , habitat and social factors affecting distance and duration of foraging trips performed during nestling rearing, recorded by visual observations in the Italian Alps. Based on 309 foraging trips from 35 pairs, we found that trips lasted 6.12 min and foraging areas were located at 175 m from the nest site on average. Trip duration was affected by snow cover (longer at intermediate cover), distance travelled and wind, while distance travelled was affected by snow cover (being higher at intermediate cover) and trip duration. Foraging individuals thus travelled farther and spent more time at areas characterized by intermediate snow cover, implying the presence of snow margins. It is likely that at such snow patches/margins snowfinches collected food for self-maintenance, besides that for their offspring, or collected more food items. Any reduction of snow cover during the breeding season, as expected under current climate warming, will severely alter foraging habitat suitability. Conserving suitable foraging habitats in the nest surroundings will be crucial to buffer such negative impacts.
... In a stochastic alpine habitat, the cost-to-benefit ratio of arriving early may be greater than in a less seasonal and more environmentally consistent low elevation habitat. At our alpine site, daytime temperatures often remain at or below 0 • C throughout the first half of May, with frequent storms and high wind speeds (Camfield and Martin, 2009;Martin et al., 2017). Therefore, both males and females may experience stabilizing selection to arrive at similar times. ...
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For migratory animals, events at one stage of the annual cycle can produce constraints or benefits that carry over to subsequent stages. Differing life-history strategies among individuals can influence the expression of these carry-over effects, leading to pronounced within-population variation in migration. For example, reproductive roles can drive spatiotemporal segregation during the non-breeding season and promote sex-specific carry-over effects, such as reproductive effort affecting autumn migration behavior. For an alpine breeding population of horned larks Eremophila alpestris in northern British Columbia, Canada, we addressed sex-specific variation in migration behavior and carry-over effects during both autumn and spring migration using light-level geolocators. Males spent more time farther north and arrived an average of 6 days earlier at the breeding site in spring. Females delayed autumn departure following greater reproductive effort, in turn demonstrating flexible migration behavior by increasing migration speed and decreasing stopover use. Males maintained autumn migration behavior regardless of reproductive effort or departure date. Finally, both sexes used staging areas in spring (average stopover = 41 days), with consequences for breeding success. Individuals that used staging areas during spring migration exhibited greater nest success and produced 1.8 more fledglings on average than those that migrated directly from their winter site. Consistent use of staging areas may allow individuals to monitor environmental conditions and optimize their breeding arrival date to acquire high-quality territories while avoiding the cost of arriving too early in a harsh alpine habitat. Overall, our results indicate: (1) sex-specific flexibility in migration strategies that carry-over to and from the reproductive period, and (2) spring staging areas may be a critical component of the annual life-cycle for alpine breeding larks. These behaviors may be particularly important for alpine and arctic birds because the stochastic nature of their breeding habitat likely selects for flexible responses to prevailing conditions.
... Nests with bigger linings were found at wetter nest sites, especially when an open water pool was closer that one meter from the nest and nest site moisture served as a proxy for local microclimate. Our finding is in line with general assumption that thermoregulatory function of the nest is important (Deeming and Reynolds 2015), especially in ground-nesting species breeding in the extreme climates of Arctic (Tulp et al. 2012) or alpine environments (Camfield and Martin 2009). Thus, Arctic shorebirds prefer to breed on slopes with a milder microclimate (Meltofte et al. 2007) and use specific lining material to reduce heat loss from nests (Reid et al. 2002). ...
Article
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Nest lining is a key component in nests of many bird species. Among ground-nesting birds with open nests, it usually consists of dry sticks and stalks creating a thermoregulatory insulating layer for the eggs. However, a bigger nest lining can attract predators and increase nest mortality. The factors influencing behavioural plasticity in birds facing the trade-off between nest lining thermoregulation and conspicuousness for predators have remained poorly understood. The Northern Lapwing Vanellus vanellus, a visibly incubating shorebird with an active nest defence against potential predators, demonstrates great variability in the size of nest lining and, at the same time, is subject to a high frequency of nest predation. We analysed the variability of nest-lining size across time and space in 915 measurements of 601 lapwing nests in South Bohemia, Czech Republic, during 2010–2015. We show that lapwing nests placed closer to small water pools with generally cooler microclimates had bigger nest lining. The size of nest linings also reflected the availability of nest lining material in the vicinity of the nest. On the other hand, there was no effect of nest position within the breeding association and distance to the nearest perch as a possible stand for predators on nest lining size. Furthermore, nest lining size did not predict nest predation rate. Our findings suggest that lapwings adjust the size of their nest lining to local microclimate conditions rather than potential predation risk which is in concordance with the thermoregulation hypothesis of the nest size in birds.
... Ground-nesting, open-cup species in these habitats may be most constrained by the environment given frequent exposure to ambient conditions and predation risk Martin & Ghalambor, 1999). We studied an alpine population of a ground-nesting songbird, the horned lark Eremophila alpestris, which can experience daily temperature fluctuations from −5 to +35°C (Camfield & Martin, 2009) and variable nest predation rates among years (range: 32.1%-83.8% nest loss; MacDonald, Camfield, Martin, Wilson, & Martin, 2016). ...
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Variation in offspring development is expected to be driven by constraints on resource allocation between growth and maintenance (e.g. thermoregulation). Rapid post‐natal development decreases predation risk to offspring, while inclement weather likely prolongs development. For taxa with parental care, parental behaviour may partially buffer offspring against extrinsic drivers like predation risk and severe weather. Using a 7‐year dataset from an alpine population of horned lark Eremophila alpestris, a ground‐nesting songbird in northern British Columbia, Canada, we investigated multiple potential drivers of variation in the duration of incubation and nestling development. Using path analysis, we evaluated the direct effects of weather, predation risk and parental care on offspring development, as well as indirect developmental “carry‐over” effects of conditions during incubation on the nestling period. Nestling period duration varied by nearly 100% (7–13 days) and incubation duration by 40% (10–14 days). Cold ambient temperatures late in the nestling period prolonged development by 1 day for every 2 days below 10°C, particularly when combined with heavy precipitation. Rapid nestling development was associated with high predation risk, and prolonging development incurred a nest survival cost (–2.3% per day). Females in good condition created nest environments that promoted rapid nestling development periods (average = 8–9 days) compared to poor condition females during harsh, early‐season conditions (10–11 days), indicating parental buffering capabilities against environmental constraints. Fledging age was weakly correlated with incubation duration (r = –0.21) suggesting minimal developmental carry‐over effects. Given high nest predation risk, immediate fitness benefits can be derived by overcoming environmental constraints and reducing development time. While predation risk was influential, inclement weather and maternal condition had stronger effects on variation in offspring development. Addressing multiple drivers of variation in key life‐history traits can provide important context for understanding life‐history theory under changing environmental conditions. A plain language summary is available for this article.
... Temperature probes and dataloggers (Thermister probe PB-5005; Tinytag Talk 2 TK4014; Gemini Data Loggers, Chichester, UK) were installed on active reed warbler nests prior to egg-laying. This technique has been used to monitor incubation behavior in a number of passerine species (Joyce et al. 2001, Camfield andMartin 2009). The installation of the data loggers involved carefully inserting temperature probes through the nest material so the tip of the probe was flush with the lining of the nest cup. ...
Article
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Climate‐driven increases in spring temperatures are expected to result in higher prey availability earlier in the breeding season for insectivorous birds breeding in wetland habitats. Predation during the incubation phase is a major cause of nesting failure in open‐nesting altricial birds such as the Eurasian reed warbler. The nest predation rate in this species has recently been shown to be substantially reduced under conditions of experimentally elevated invertebrate prey availability. Food availability near the nest may be an important determinant of adult incubation and nest defence behaviours during the incubation period. We used two experimental studies to compare incubation behaviour and nest defence in food‐supplemented and unsupplemented adult Eurasian reed warblers during the incubation phase. In the first study we measured nest defence behavioural responses to a taxidermic mount of a native predator (a Stoat, Mustela erminea). In the second study we used temperature loggers installed in nests to measure breaks in incubation as a measure of nest vulnerability. Food‐supplemented birds responded aggressively to the presence of a predator more quickly than those in the unsupplemented group, suggesting they are closer to their nest and can more quickly detect a predator in the vicinity. Food‐supplemented birds also had shorter breaks in incubation (both in terms of maximum and mean off‐bout durations), presumably because they were foraging for shorter periods or over shorter distances from the nest. This study therefore identifies the behavioural mechanisms by which changes in food availability may lead to changes in nest survival and thus breeding productivity, in open‐nesting insectivorous birds. This article is protected by copyright. All rights reserved.
... When analysing effects of ambient temperature on daily male feeding rate and female nest attendance (models D1-2), temperature was used as a quadratic term (using 'poly'-function), because preliminary analyses indicated a non-linear relationship (see also Conway & Martin 2000a, Camfield & Martin 2009). ...
Article
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Most bird species show biparental care, but the type of care provided by each sex may differ substantially. In particular, during the incubation phase in passerines, females perform most or all of the incubation, while the male cares for the brood indirectly by feeding the female. However, detailed descriptions of this male investment during the incubation period are missing. Here, we quantitatively describe female nest attendance and male incubation feeding throughout the ~14‐day incubation period in a population of Eurasian Blue Tits Cyanistes caeruleus breeding in nest‐boxes. Males and females progressively increased their daily activity at the nest over the incubation period. The amount of day‐time incubation, measured as the proportion of the active day (time interval between first nest‐box exit in the morning and last entry in the evening) a female spent inside the nest‐box, varied between 52‐60% with an average of 55% per day. The frequency of male incubation feeding varied between 0‐74 times per day with an average of 12 feeds per day. Both male feeding rate and female nest attendance were highest in the morning and declined rapidly throughout the day. Females were more likely to be off the nest during the warmest periods (15‐21 °C), as expected based on thermal needs of the developing embryos, but also during the coldest periods (2‐5 °C), presumably due to the energetic needs of the female. This was despite the fact that males fed their females more often at the nest when ambient temperatures were low. Females that received more feeds incubated more and their off‐nest bouts were shorter after a feed. The observed variation in female incubation and in male feeding rate was not linked to individual age or to variation in measures of reproductive success. However, direct observations showed that in some pairs a substantial amount of male feeding by males occurred outside the nest‐box. This suggests that the true male investment might have been underestimated, here and in previous studies. This article is protected by copyright. All rights reserved.
... The timing of snowmelt varies annually, with patches of snow persisting through most of June, and the overall length of the growing season is considerably reduced in comparison to low-elevation habitats used by these species (Camfield et al. 2010, MacDonald et al. 2014). Daily breeding-season temperatures fluctuate widely at the site, dropping near or below freezing on most nights and sometimes exceeding 408C at ground level during the day (Camfield and Martin 2009, MacDonald et al. 2013, 2014). Strong winds and storms involving snow or rain occur throughout the nesting period, with more frequent and extreme events earlier in the breeding season (Figure 1). ...
Article
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We examined the impact of daily and severe multiday weather events on nest survival of Horned Larks (Eremophila alpestris) and Savannah Sparrows (Passerculus sandwichensis) breeding sympatrically in alpine habitat. The two species' thermal regimes varied. The breeding season of Horned Larks was ∼2°C colder and had more precipitation and more storms than that of Savannah Sparrows, which initiated laying 2 wk later. The breeding season of Savannah Sparrows was, on average, 27% shorter than that of Horned Larks. Overall daily nest survival (DNS) was similar for the two species, but Savannah Sparrows had more failure due to abandonment (33% of nests) than Horned Larks (10%). Using Program MARK and Akaike's Information Criterion model selection to evaluate effects of daily and cumulative temperature and precipitation on DNS, we found no direct effect of daily temperature on nest survival, but nest survival declined in colder years for both species. For Horned Larks, the top nest survival models included a decline in DNS with increasing nest age and number of storm events, and a temperature × storm interaction. Daily nest mortality (DNM) increased by 8-9× over background failure levels during cold storms (average = 5°C), but there was little change in DNM during warmer storms (8°C). For Savannah Sparrows, the top nest survival models included a negative influence of cumulative precipitation. The top model's predicted DNM was ∼4.6× higher after ≥2 days of precipitation than following days without rain. Both species coped well with the range of daily temperatures and single days of precipitation typical of alpine habitats, but the earlier-breeding Horned Larks were more susceptible to storm events, whereas extended precipitation events most strongly affected Savannah Sparrow nest survival. The ability of these songbirds to persist in alpine habitats may depend partly on the proportion of "cold" and "warm" storm events in future alpine climates.
... Most songbirds exhibit this incubation strategy, where only one parent (usually the female) incubates, and, therefore, egg temperatures fluctuate as females depart from and return to nests (Deeming 2002). In most environments, ambient temperatures during the breeding season are outside the optimal range for embryonic development (Camfield and Martin 2009) so incubating females should attempt to maintain embryonic temperatures within this range (Haftorn 1988). However, on-bout duration may be constrained by the energy budgets of females (Ardia et al. 2009). ...
Article
Because extended incubation recesses, where incubating songbirds are away from nests for periods much longer than usual, occur infrequently, they have been treated as outliers in most previous studies and thus overlooked. However, egg temperatures can potentially fall below the physiological zero temperature during extended recesses, potentially affecting developing embryos. As such, evaluating extended recesses in an ecological context and identifying their possible fitness effects are important. With this aim, we used iButton data loggers to monitor the incubation behavior of female Blue Tits (Cyanistes caeruleus) and Great Tits (Parus major) during two breeding seasons in central Spain. We classified incubation recesses as extended if they were more than four times the mean recess duration for each species. Extended incubation recesses occurred more frequently in 2012 when females exhibited poorer body condition. Female Blue Tits had more extended incubation recesses than female Great Tits and, for both species, more extended recesses occurred at the beginning of the breeding season. Both nest attentiveness and average minimum nest temperature decreased when at least one extended recess occurred. Incubation periods averaged 4 d longer for nests where females had at least one extended recess, potentially increasing predation risk and resulting in lower-quality nestlings. Overall, our results suggest that extended recesses may be more common among songbirds than previously thought and that, due to their effects on egg temperatures and attentiveness, they could impose fitness costs.
... More frequent re-heating of eggs and shorter off-nest bouts likely buffer the faster drop of egg temperature at lower ambient temperatures (as shown in great tits: Boulton and Cassey 2012). In addition, prolonged recess would result in a net loss of female energy for re-warming the (colder) eggs (Camfield and Martin 2009). However, there are studies which found no effect of ambient temperature on egg temperature (e.g. ...
Article
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Incubation is an important aspect of avian life history. The behaviour is energetically costly, and investment in incubation strategies within species, like female nest attentiveness and the feeding by the non-incubating partner during incubation, can therefore vary depending on environmental and individual characteristics. However, little is known about the combined effect of these characteristics. We investigated the importance of ambient temperature, habitat quality, and bird age on female incubation behaviour and male feeding of the incubating female (incubation feeding) in blue tits Cyanistes caeruleus, a socially monogamous songbird. An increase in ambient temperature resulted in a higher nest temperature, and this enabled females to increase the time off the nest for self-maintenance activities. Probably as a consequence of this, an increase in ambient temperature was associated with fewer incubation feedings by the male. Moreover, in areas with more food available (more deciduous trees), females had shorter incubation recesses and males fed females less often. Additionally, males fed young females more, presumably to increase such females' investment in their eggs, which were colder on average (despite the length of recesses and female nest attentiveness being independent of female age). Male age did not affect incubation feeding rate. In conclusion, the patterns of incubation behaviour were related to both environmental and individual characteristics, and male incubation feeding was adjusted to females' need for food according these characteristics, which can facilitate new insights to the study of avian incubation energetics. Significance statement: Parents often invest a substantial amount of energy in raising offspring. How much they do so depends on several environmental factors and on the extent they cooperate to raise the offspring. In birds, males can feed incubating females, which may allow females to stay longer on the nest, which, in turn, may ultimately improve reproductive success. The interplay between environmental factors and such incubation feeding on incubation attendance has, however, received little attention. Here, we show that favourable circumstances (higher ambient temperature and food availability) allowed incubating blue tit females to increase the time off the nest to improve self-maintenance and males to feed them less, whereas males also fed inexperienced partners more often. Thus, we show a concerted effect of several environmental and intrinsic factors on parental effort during incubation, which will help to improve the general understanding of avian incubation and parental care.
... Wildlife living at high elevations must be able to cope with high winds, cold temperatures and desiccation, since often little precipitation originates from rainfall and it drains quickly through the shallow soils with limited organic matter (see Chapter 3). Although alpine soils are normally cold, daily summer temperatures near the ground range from a few degrees below freezing to almost 50ºC [19,20]. Thus, during mid day, dessication and overheating can be a problem for mountain species. ...
Chapter
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Mountain ecosystems consist of alpine zones characterized by rugged, partially vegetated open terrain with snowfields and rocky ridges above montane forests. These alpine grasslands and shrublands, sub-alpine parkland and montane forest habitats are high energy environments characterized by prolonged snow cover, steep terrain, extremes of heat and cold, and intense ultraviolet radiation. With increasing elevation, time for growth and reproduction decreases, environmental conditions become harsher with increasing stochasticity; at the highest elevations, hypoxic conditions add additional energetic living costs. For plants, dispersal of pollen, seeds or ramets may be limited by topography, weather conditions and patchy habitats where access to nutrients may be limited. These factors result in short, intense growing and breeding seasons. Only a few plants and animals live exclusively in the alpine, while many mountain species breed in both alpine and lower elevation habitats. To cope with their difficult environmental conditions, plants and wildlife living in mountain habitats have adopted a slower lifestyle where they may produce fewer offspring each year compared to populations at low elevations, but many live longer and thus have more years to breed and replace themselves. The compression of several habitat types and variable environmental conditions within small spatial areas often results in high species endemism and biodiversity in mountain areas. High elevation ecosystems are used by migrating wildlife after breeding, a time when mountain habitats offer rich food resources and when productivity in many low elevation habitats has declined. Thus, we need to include life history periods outside the breeding season to accurately evaluate the biodiversity of mountain habitats. Connectivity is a key ecological process for high elevation wildlife populations. Connectivity needs to be maintained (1) among patchy habitat islands for breeding populations, (2) along mountain corridors for north-south migrants, and also (3) between alpine and adjacent lower elevation habitats and valley bottoms for both breeding populations and migrants. Many European and Asian mountain ecosystems are heavily altered by agriculture, forestry and intense recreational activities such as skiing developments. Although most alpine habitats in North America appear relatively intact, ecological change is also
... Relatively stable lenght of off-bouts during a day is in 346 agreement with the hypothesis that incubating females modify their behaviour (i.e. foraging 347 bouts) so as to minimize the cost of rewarming eggs and the risk of cooling the eggs through 348 by varying the frequency rather than length of off-bouts (Camfield & Martin 2009, MacDonald 349 2014. The observed drop of off-bout lenght at the end of daily activity might reflect prior 350 sufficient food supplementation for overnight incubation (Moreno 1989, Smith et al. 1989, 351 Chalfoun & Martin 2007, Lothery et al. 2014. ...
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Agricultural intensification may increase an impacts of predators on the reproductive performance of declining populations of farmland birds. Still, there is little definitive evidence of nest success and predator identity in intensive arable fields. In order to clarify whether nest predators really contribute to declines in farmland ground nesting birds, I used video-monitoring to identify nest predators and quantify nest success in the Skylark (Alauda arvensis) and Lapwing (Vanellus vanellus). Both species share common nesting habitats in sparsely vegetated arable fields, but their life histories suggest different vulnerabilities to nest predation. Results showed very low nest success in the Skylark, but relatively high success in the Lapwing. Skylark nests were vulnerable to all local predators, while it seems that Lapwings can avoid avian predators. The species composition of predators and patterns in nest predation rates mostly differed from those reported from Western Europe. Because of expected differences in predator identity and nest survival among nesting habitats and regions, I further quantified nest success and identified nest predators for a high-density population of Skylarks as well as Woodlarks (Lulllula arborea) breeding in more natural heath and grassland habitats in the Netherlands. Populations of both species co-occur in this area and their nests are similar targets for local predators; even so their nest predators might differ, because these larks differ in the selection of their nest sites. My results suggest that Skylark nests located in open sites were preyed upon mainly by red foxes (Vulpes vulpes), while the main predators of Woodlark nests, located generally closer to trees, were Carrion Crows (Corvus corone). Changes in agricultural practices, especially shifts from spring-sown to autumn-sown crops, can limit the number of breeding attempts of Skylarks. Under these circumstances, Skylarks are forced to shift to different breeding sites or habitats. In spite of the seasonal shift in nest sites in my study, nest predation rates did not show a clear seasonal trend; however, the proportion of predation attributed to birds decreased along with vegetation growth. My results suggest that the recently increasing area of maize fields in particular provide an attractive, yet risky, nesting habitat for Skylarks, especially late in the season when autumn-sown crops are too dense. Nest proximity to field edges may also have a negative influence on breeding productivity, with nests placed closer to edges experiencing higher rates of nest predation. I found that Skylarks seem to avoid areas close to field edges in spite of the comparatively low predation cost associated with nesting there. Variation in nest predation risk during the breeding period may be an important source of natural selection on parental behaviour. Skylark females spent more time attending clutches in the early morning and evening, with more frequent recesses during the afternoon. Moreover, this diurnal variation was dependent on (i.e. interacted with) ambient temperature and vegetation characteristics at the nest site (height and concealment). This suggests that the way incubation time is allotted during the day may be equally as important as the total amount of time spent incubating.
... Understanding why the timing and amount of incubation varies so substantially in Mountain Bluebirds will require further work and will be a major challenge, given the myriad of potentially interacting factors involved (Magrath 1990, Hébert 2002. Weather conditions before and during laying, including not only ambient temperatures, but also precipitation and especially wind, are likely to have a major impact on incubation during laying (Ardia et al. 2006, see also Conway and Martin 2000, Camfield and Martin 2009, Wang and Beissinger 2009. Other probable influences include a female's inherent condition/quality, breeding experience, and hormonal profiles (Vleck 2002, Sockman et al. 2006. ...
Article
Females in many bird species reportedly begin incubation prior to clutch completion, but the nature of such incubation and the degree to which it varies among females remains undescribed for almost all species. We used continuous recording of nest-cup temperatures to document incubation effort during egg laying at 57 Mountain Bluebird (Sialia currucoides) nests in a high-elevation Wyoming population. We then asked whether such effort predicted the degree to which eggs hatch asynchronously. Although substantial egg heating could begin abruptly late in laying (previously reported as the norm for this species) or even after clutch completion, we found that most (>90%) females began incubation gradually, engaging in a few (usually 1–8), brief (<10 min) bouts of heating on the day they laid their first or second egg. Thereafter, females varied markedly in when they increased incubation effort and by how much. The onset of nocturnal incubation also varied, with females beginning to incubate at night after laying their prepenultimate, penultimate, or last egg and not always initially incubating through the night. As an index of the total amount of heat applied to eggs during laying, we calculated the cumulative number of degrees by which nest-cup temperatures exceeded the threshold temperature required for embryonic development. This value varied by more than 150-fold between nests and explained >50% of the variation in hatching asynchrony. Our results thus provide strong support for the widely held, but rarely tested, assumption that parent birds can have substantial control over the degree of hatching asynchrony by varying the amount of incubation done prior to clutch completion.
Chapter
Alpine birds face many challenges to live and breed at high elevations, including temperature extremes, strong winds, hypoxia, and limited opportunities to reproduce. To cope with these challenges, alpine birds have developed physiological, morphological, and behavioural adaptations, as well as potentially adopting a slower lifestyle where reduced annual reproduction is balanced by greater longevity. Alpine birds may benefit from reduced ecological constraints, such as lower interspecific competition, parasitism, and habitat loss compared to lower elevations. Here, we outline the abiotic stressors that limit avian life at high elevations, and examine the structural, physiological, genetic, and behavioural adaptations that enable birds to live and breed in alpine ecosystems. We discuss the ecological dynamics acting on birds at high elevations and highlight significant knowledge gaps in high mountain ecology globally. We contextualize high elevation adaptations within a life-history framework, and discuss how these adaptations may make alpine birds particularly vulnerable to climate change.
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Across taxa, offspring size traits are linked to survival, and life-time fitness. Inclement weather can be a major constraint on offspring growth and parental care. Despite the adaptive benefits of larger offspring, we have a limited understanding of the effects of severe environmental conditions across developmental stages and how coping strategies differ among species. We assessed the influence of inclement weather on offspring size and mass traits within populations of three alpine breeding songbirds in British Columbia: (1) horned lark (Eremophila alpestris), (2) dark-eyed junco (Junco hyemalis), and (3) savannah sparrow (Passerculus sandwichensis). Specifically, we investigated at which stages during early-life development offspring are most vulnerable to inclement weather and whether thresholds exist in the developmental response to severe weather events. Across species, we identified two critical periods that best predicted offspring size: (1) clutch initiation, and (2) the nestling stage. Colder temperatures experienced by the female during clutch initiation were associated with larger, heavier offspring in horned larks but smaller offspring for savannah sparrows, indicating the potential for maternal effects, albeit acting through different mechanisms. Additionally, horned lark offspring were resilient to colder average temperatures during the nestling stage but were vulnerable to extreme cold events and multi-day storms. In contrast, dark-eyed junco nestlings were robust to storms, but smaller size and mass traits were associated with lower daily maximum temperatures (i.e., more mild temperature challenges). We suggest species differences may be linked to life-history traits, such as: (1) the thermoregulatory benefits of larger body mass in horned larks, (2) the benefits of greater nest cover to buffer dark-eyed junco against precipitation events, and (3) delayed clutch initiation for savannah sparrows to limit exposure to cold storms. We provide evidence for stage-specific impacts of inclement weather on offspring development with implications for reproductive success. These results advance our understanding of early-life resilience to stochastic environments, as we may be able to predict differences in the vulnerability of alpine species to increasingly variable and severe weather conditions.
Article
Intermittently incubating birds alternate between sessions of egg warming and recesses for foraging during the day, but stay on the nest continuously at night. Hence, energy costs of nocturnal incubation (which increase during longer and colder nights) cannot be replenished until the next day. Night conditions might therefore be expected to affect morning incubation behaviour the day after. We tested this prediction by exploring latitudinal and seasonal trends in characteristics of the first recess in Eastern Bluebirds Sialia sialis over a 1400 km latitudinal gradient in the continental United States of America. The time from civil dawn to leaving the nest (latency) increased with latitude early in the breeding season, but decreased with latitude late in the season. Birds breeding at higher latitudes also took longer first recesses throughout the season, which led to a larger drop in nest temperature. At the local scale, birds rose earlier after longer nights if the night was also cold, but night length did not predict latency following warm nights. The first recess was longer if the night was warmer, probably because birds could replenish reserves at lower risk of low egg temperature. Our study shows that characteristics of the night led to behavioural changes in features of early morning incubation that were evident at both continental and local scales. These responses also affected nest temperature. Hence, night conditions carry over to incubation behaviour the following morning, which in turn may impose thermal constraints on embryonic development.
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Incubating birds must trade-off leaving the nest to forage with staying on the nest to maintain optimal temperatures for developing embryos. This trade-off is expressed through incubation behavior, which can be heavily influenced by climate, food availability, attentiveness of their mates, and nest predation risk. Comparative studies across species have shown that incubation behavior varies across latitude, but few studies have explored how incubation behavior varies across sites within species. We might expect incubation behavior to be flexible and respond to local environmental challenges; alternatively, behavior may be relatively fixed and vary little across a species’ range. We explored four incubation behaviors (male feeding rate, female off-bout duration, female off-bout frequency, and the proportion of time incubating females spent on the nest) in a widespread songbird, the yellow warbler (Setophaga petechia), breeding at a temperate and subarctic site. As temperatures warmed at both sites, males fed females less often, and as male feeding rates decreased, off-bout durations and frequencies increased causing the proportion of time on the nest to decrease. While incubation behaviors changed in similar ways between sites, off-bout durations shortened with increasing male feeding rates most strongly at the temperate site. Overall, these results show flexibility in incubation behaviors in response to different environmental cues, which likely minimize costs associated with provisioning incubating parents and maintaining warm nest temperatures, and suggests that male feeding may be especially important for breeding in cold regions.
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We examined timing of breeding, nest site selection and nest survival of Horned Larks (Eremophila alpestris), Savannah Sparrows (Passerculus sandwichensis) and American Pipits (Anthus rubescens) in an alpine habitat on Hudson Bay Mountain, BC, Canada in 2003–2007. These species partitioned their nesting niches temporally and spatially. We compared nest site characteristics among species using one-way ANOVA and logistic regression. Horned Larks (n = 103 nests) initiated breeding 2 weeks earlier (mean = 1 June) than Savannah Sparrows (n = 52, mean = 14 June) and American Pipits (n = 38, mean = 11 June). Horned Larks and American Pipits nested at similar elevations (means = 1714 and 1719 m, respectively); however, lark nests were more exposed (greater bare ground, rock and lichen/moss cover), with minimal nest concealment, while pipit nests, built into banks and soil mounds, had high concealment. Savannah Sparrows nested at lower elevation (mean = 1649 m) with greater dead vegetative cover. We assessed intraspecific habitat preferences for Horned Larks and Savannah Sparrows using logistic regression; both species chose nest sites with greater availability of their preferred habitat characteristics. We used model selection to evaluate effects of nest site characteristics, nest age, season and year on daily nest survival (DNS). Horned Larks displayed the lowest DNS of 0.954 ± 0.009 (n = 189 nests), which varied with year, season and nest age, but was not influenced by site characteristics. In contrast, DNS was highest for Savannah Sparrows (0.961 ± 0.014, n = 89) with strong responses to nest concealment, year and nest age. American Pipits exhibited an intermediate DNS (0.959 ± 0.009, n = 38), which varied with overhead concealment and elevation. Despite the simple structure of the alpine habitat, there was significant niche differentiation in nest site choices among these species. Preferences for nest concealment were positively related to nest survival in Savannah Sparrows and American Pipits but not Horned Larks, indicating how a common environment can differentially influence behavior and demography.
Conference Paper
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In patchy forest areas, the size of the forest patch where birds breed has a strong influence on their breeding success. However, the proximate effects contributing to lowering the breeding success in small forest patches remain unclear; and a shortage of crucial resources in those forest patches has been suggested to account in some degree for this failure. With the aim to further investigate this issue, we have monitored the breeding cycle of blue and great tits in three 'large' forest patches (ranging between 26.5 and 29.6 ha) and twelve 'small' forest patches (ranging between 1.1 and 2.1 ha) in a Mediterranean area in central Spain, during three years (2011-2013). We also recorded the nestling diet inside the nest-boxes with the aid of handy-cams. Only males significantly differed between forest patch size categories; being on average younger and with better body condition in small patches for great and blue tits respectively. Reproductive traits did not vary between forest patch size categories, but the body condition of blue tit nestlings and the size of great tit nestlings did, being significantly better and larger respectively in large forest patches. The recruitment rate of blue tit nestlings was also higher in large patches. Regarding nestling diet, blue tits did not differ but great tits did, delivering a larger amount of caterpillars in large forest patches. Most variation in the reproductive traits occurred between years, probably due to annual differences in environmental conditions. This study suggests that food supply could be limiting the breeding success of birds above all in small patches, but also in large patches under particular environmental conditions.
Article
Elevational gradients provide powerful natural systems for testing hypotheses regarding the role of environmental variation in the evolution of life-history strategies. Case studies have revealed shifts towards slower life histories in organisms living at high elevations yet no synthetic analyses exist of elevational variation in life-history traits for major vertebrate clades. We examined (i) how life-history traits change with elevation in paired populations of bird species worldwide, and (ii) which biotic and abiotic factors drive elevational shifts in life history. Using three analytical methods, we found that fecundity declined at higher elevations due to smaller clutches and fewer reproductive attempts per year. By contrast, elevational differences in traits associated with parental investment or survival varied among studies. High-elevation populations had shorter and later breeding seasons, but longer developmental periods implying that temporal constraints contribute to reduced fecundity. Analyses of clutch size data, the trait for which we had the largest number of population comparisons, indicated no evidence that phylogenetic history constrained species-level plasticity in trait variation associated with elevational gradients. The magnitude of elevational shifts in life-history traits were largely unrelated to geographic (altitude, latitude), intrinsic (body mass, migratory status), or habitat covariates. Meta-population structure, methodological issues associated with estimating survival, or processes shaping range boundaries could potentially explain the nature of elevational shifts in life-history traits evident in this data set. We identify a new risk factor for montane populations in changing climates: low fecundity will result in lower reproductive potential to recover from perturbations, especially as fewer than half of the species experienced higher survival at higher elevations.
Article
During incubation, tropical passerines have been shown to have lower levels of nest attentiveness than their counterparts at north temperate latitudes, spending a higher percentage of daylight time off the nest. This difference has been interpreted as evidence of parental restraint; tropical birds allocate more time to daily self-maintenance, perhaps preserving their higher annual survival rates and future breeding potential. But such comparisons are susceptible to the confounding effects of day length variation, because a given amount of time spent off the nest will account for a greater percentage of daylight time near to the equator than at high latitudes during spring and summer. Based on a pattern of increasing day length between 0° and 70°N, we show that the impact of this bias is likely to be small where sites are separated by less than 30°–40° of latitude, but should increase substantially both with latitudinal span and distance from the equator. To illustrate this effect, we compared nest attentiveness in two congeners breeding at 1°S and 52°N. During incubation, Stripe-breasted Tits Parus fasciiventer in Uganda had a shorter working day (time from emerging to retiring) than north temperate Great Tits P. major, and spent a higher percentage of daylight time off the nest (32 %) than Great Tits in the UK (24 %). However, this difference was almost wholly explained by the latitudinal difference in day length; the amount of time spent off the nest differed by just 10 min day−1 (
Article
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Elevational gradients provide powerful natural systems for testing hypotheses regarding the role of environmental variation in the evolution of life-history strategies. Case studies have revealed shifts towards slower life histories in organisms living at high elevations yet no synthetic analyses exist of elevational variation in life-history traits for major vertebrate clades. We examined (i) how life-history traits change with elevation in paired populations of bird species worldwide, and (ii) which biotic and abiotic factors drive elevational shifts in life history. Using three analytical methods, we found that fecundity declined at higher elevations due to smaller clutches and fewer reproductive attempts per year. By contrast, elevational differences in traits associated with parental investment or survival varied among studies. High-elevation populations had shorter and later breeding seasons, but longer developmental periods implying that temporal constraints contribute to reduced fecundity. Analyses of clutch size data, the trait for which we had the largest number of population comparisons, indicated no evidence that phylogenetic history constrained species-level plasticity in trait variation associated with elevational gradients. The magnitude of elevational shifts in life-history traits were largely unrelated to geographic (altitude, latitude), intrinsic (body mass, migratory status), or habitat covariates. Meta-population structure, methodological issues associated with estimating survival, or processes shaping range boundaries could potentially explain the nature of elevational shifts in life-history traits evident in this data set. We identify a new risk factor for montane populations in changing climates: low fecundity will result in lower reproductive potential to recover from perturbations, especially as fewer than half of the species experienced higher survival at higher elevations. © 2015 Cambridge Philosophical Society.
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Incubating birds can incur high energetic costs and, when faced with a trade-off between incubation and foraging, parents may neglect their eggs in favor of their own somatic needs. Extended incubation recesses are an example of neglect, but they are often treated as outliers and largely overlooked in studies of incubation behavior. We studied incubation rhythms of Horned Larks (Eremophila alpestris) on Hudson Bay Mountain, British Columbia, Canada, during four breeding seasons. Incubation recesses averaged 10.92 ± 0.38 min (N= 4076 2-h periods), but we observed 70 extended recesses, ranging from 59 to 387 min in duration, at 35 nests. Although rare (<1% of all daytime recesses), extended recesses occurred in all 4 yr, were longer and more frequent in colder years (60% occurred in the two coldest years), and often occurred during inclement weather (39% occurred during three storm events). Extended recesses did not appear to compensate for long attendance periods because extended recess duration was not correlated with the duration of previous on-bouts (P= 0.10, N= 70) or the mean on-bout duration of the previous 2-h period (P= 0.36, N= 70). Rather, extended recesses seemed to reflect a shift in parental investment away from their eggs and toward self-maintenance when faced with energetically stressful conditions. Extended recesses may have reduced embryo viability; egg-hatching rates were 91 ± 2.4% for nests where females did not take extended recesses and 81 ± 4.2% for nests where females did take extended recesses (P= 0.02, N= 56 nests). Extended recesses during incubation are rare events, but they may represent an important mechanism that allows birds to breed successfully in energetically challenging conditions.
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Highlights ► We examined functions of adult female begging during incubation in sub-Arctic breeding yellow warblers. ► Incubating adult females make chip calls, flutter their wings and change postures in the nest when begging. ► Female begging intensity increased with longer time intervals between male feedings, especially during cold weather. ► Male feeding rate increased in response to female begging at warm, but not at cold, ambient temperatures. ► Frequent male feedings allowed females to spend more time on their nests.
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During the 1994 and 1995 breeding seasons, we examined the orientation of Vesper Sparrow (Pooecetes gramineus) and Horned Lark (Eremophila alpestris) nests relative to vegetative cover in the Chilcotin grasslands of central British Columbia. To investigate the effects of nest placement on nest microclimate, we compared nest temperatures with (1) different orientations relative to single clumps of vegetative cover, (2) different orientations relative to multiple clumps of vegetative cover, and (3) different amounts of vegetative cover. Vegetation was located on the southwest side (180-2600) of 87 percent of nests of both species. The distribution of single clumps of vegetation (77 percent of nests) around nests of both species in both years differed significantly from a uniform distribution. Nests with either a single clump of vegetation on the southwest side or with more than one clump of vegetation on the southeast to southwest side had lower temperatures than did nests with vegetation on other sides; these nests also remained above the temperature that may be lethal to developing embryos (38 C) for shorter periods of time during the day than did other nests. Nests without vegetation on the east side warmed up more rapidly in the morning than did nests with vegetation on the northeast or southeast side. The height of the vegetation clump and the amount of cover it provided also influenced nest temperatures. Nests with more than 90 percent cover exceeded 38 C for only 1.25 hours at midday, whereas nests with less than 20 percent cover exceeded 38 C for 4.25 hours. The pattern of nest orientation displayed by Vesper Sparrows and Horned Larks in this study appeared to reflect selection for thermally advantageous nest sites.
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The effects of predation risk, body condition of females, and microclimate at the nest site on timing and length of incubation recesses at 30 nests of white-tailed ptarmigan Lagopus leucurus were examined. Incubation patterns in 1994 (an early year) were also compared to those of 1995, an unusually late spring with low temperatures. Data on incubation schedules were obtained by placing programmable temperature data-loggers in nests and by direct observation of incubating females. Some egg depredation was associated with movements of hens to and from nests, but there were no apparent differences in risk between crepuscular recesses and daytime recesses. Ptarmigan showed high nest attentiveness (>90%) in both years of the study but took significantly more recesses of longer duration in 1995 than in 1994. This suggests that the amount of recess time was affected by body condition of the female which was lower during incubation in 1995. The overall number of recesses per day did not vary according to cover at the nest site; however, females with nests that had no overhead cover did not leave during the warmest part of the day. It is suggested that timing of recesses in this population of ptarmigan is related to microclimate and body condition, rather than being a strategy to avoid predation.
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At temperatures below 28"C, rate of oxygen consumption (vjo2) of Zebra Finches (Poephila guttuta) incubating eggs averaged 20% higher than the \ioz of non-incubating Zebra Finches sitting in a nest at the same temperature. This increase represents the energetic cost of incubation. The O,, of non-incubating birds sitting in a nest was lower than values reported for birds perched in the open at the same temperature. In the Zebra Finch, the ameliorating effects of the nest microclimate approximately compensate for the increment in metabolic rate due to incubation. The energetic cost of incubation increased when birds had to rewarm cold eggs. Incubating birds responded to artificially cooled eggs by elevating their metabolic rate and increasing heat flow to the clutch. The pattern of adult attentiveness at the nest determines the number of times and amount by which the eggs must be rewarmed. Because it is energetically more expensive to rewarm eggs than to maintain temperature once the eggs are warm, the cost of incubation de- pends in part on the attentiveness pattern. Reproduction, especially the care of eggs and young, places special demands on the way birds allocate available energy. Various techniques have been used to estimate the energetic costs associated with territorial defense (Stiles 1971, Wolf and Hainsworth I971), nest building (Collias and Collias 1967, Withers 1977a), egg production (King 1973), and the feeding of nestlings (Utter and Lefebvre 1973). These activities, to- gether with incubation of the eggs, include most of the time and energy that birds de- vote to reproductive activities. However, the costs of incubation, an activity that takes up a significant portion of the reproductive cycle, are difficult to measure and have been the subject of controversy (Kendeigh
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We examined simultaneously incubation rhythms and mass loss of 16 female Common Goldeneyes (Bucephala clan&a). On average, female goldeneyes spent 8 1% of the day incubating eggs, and took 2.7 recesses per day, each lasting an average of 114 min. Females began incubation approximately 20% heavier than the lowest body mass they reached over the incubation period, a slightly greater mass loss than predicted for ducks their size. Goldeneye incubation behaviors were similar to those reported for other Mergini, and were consistent with the general relationship between body size and incubation behavior in waterfowl. Females differed in how they varied their incubation behavior in response to incubation patterns on the previous day and environmental factors, although females typ-ically responded to warmer temperatures by spending more time off the nest. Female golden-eyes appeared to manage their mass loss by modifying their incubation behavior. Females tended to lose less mass on days following more substantial mass loss, and once females approached their minimum mass they spent more time off the nest. However, not all females were successful in this approach. Two females may have deserted their nests because they had relatively high mass loss (>20%) and reached a low body mass (about 600 g), and thus could not maintain incubation sufficient to hatch their eggs without putting themselves at further risk.
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Life history responses to environmental conditions include a combination of fecundity–survival schedules and behavioral strategies that yield the highest fitness in a given environment. In this study, we examined the pattern of covariation in avian life history strategies along an elevational gradient by comparing variation in life history traits, including most components of parental care, between phylogenetically paired taxa from low-and high-elevation sites. We found that high-elevation species had significantly lower annual fecundity but provided greater parental care to their offspring. However, a strong negative relationship between offspring number and duration of parental care along the elevational gradient suggested that high-elevation species were shifting investment from offspring number toward offspring quality. Although adult survival did not differ between high-and low-elevation species, higher juvenile survival may have compensated for lower annual fecundity in high-elevation species. The elevation at which breeding occurred strong-ly influenced the partitioning of parental behavior between sexes. Male participation in nestling provisioning was significantly greater in high-elevation species. In turn, altitudinal variation in the frequency of biparental care closely covaries with the intensity of sexual selection, ultimately resulting in the strong elevational pattern of sexual dimorphism. More-over, elevational variation in costs of development and maintenance of secondary sexual traits constitutes an additional effect on fecundity–survival schedules along elevational gradients. Thus, a trade-off between fecundity and parental care, and associated interactions among morphological, life history, and behavioral traits play important roles in the evolution of life history strategies in birds.
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— Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of food; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compensate for shorter off-bouts by taking more of them (thus shorter on-bouts) to obtain needed energy for incubation. Nest predation also explains significant variation in incubation behavior among passerines: Species that endure high nest predation have evolved an incubation strategy (long on- and off-bouts) that minimizes activity that could attract predators. Nest substrate explained additional variation in incubation behavior (cavity-nesting birds have shorter on-bouts and make more frequent nest trips), presumably because nest predation and/or temperature varies among nest substrates. Thus, nest predation can influence reproductive effort in a way previously not demonstrated–by placing a constraint on parental activity at the nest. Incubating birds face an ecological cost associated with reproductive effort (predation of entire brood) that should be considered in future attempts to explain avian life-history evolution.
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As ground nesting homeotherms, alpine and arctic birds must meet similar physiological requirements for breeding as other birds, but must do so in more extreme conditions. Annual spring snowfall and timing of snow melt can vary by up to 1 month and daily temperatures near the ground surface vary from below freezing to over 45°C in alpine and arctic habitats. Species breeding in these environments have various behavioral, physiological, and morphological adaptations to cope with energetically demanding conditions. We review the ways birds cope with harsh and variable weather, and present data from long term field studies of ptarmigan to examine effects of spring weather on reproduction. In variable but normal spring conditions, timing of breeding was not influenced by snow melt, snow depth or daily temperatures in the alpine, as breeding did not commence until conditions were generally favorable. Arctic ptarmigan tended to vary breeding onset in response to spring conditions. Generally, birds breeding in alpine and arctic habitats suffer a seasonal reproductive disadvantage compared to birds at lower latitudes or elevations because the breeding window is short and in late years, nest failure may be high with little opportunity for renesting. Coping mechanisms may only be effective below a threshold of climactic extremes. Despite strong resilience in fecundity parameters, when snowmelt is extremely delayed breeding success is greatly reduced. Alpine and arctic birds will be further challenged as they attempt to cope with anticipated increases in the frequency and severity of weather events (climate variability), as well as general climate warming.
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The thermal environment has pronounced effects on the energy costs of thermoregulation and affects an animal's allocation of energy to self-maintenance and parental care. Consequently, the selection of reproductive periods, breeding habitats and nest-sites with a favourable microclimate can be advantageous, especially for birds breeding in harsh environments. In this study on Alpine Water Pipits (Anthus spinoletta), we evaluate the importance of spatial and temporal factors on thermoregulatory costs by combining laboratory measurements of metabolic rates under various temperatures with standard operative temperatures (Te~) recorded in the field in different microhabitats. Using these measurements we estimate the thermal and energetic consequences of nest locality and timing of reproduction. Our results show: (1) In the morning, Te~ values were much higher on the east-north-east (ENE) slope of a valley than on the west-south-west (WSW) slope; in the afternoon this pattern was reversed. As a consequence, energy costs (Ehour) for thermoregulation on the ENE slope were up to 0.6 RMR (resting metabolic rate at night) lower than on the WSW slope during morning hours and about 0.8 RMR higher during afternoon hours. (2) During the incubation and nestling phases of first and second broods, total energy expenditure for thermoregulation in the daytime (Edaytime) was 0.2-0.3 RMR higher on the ENE slope than on the WSW slope. (3) Within slopes, Edaytime was lower during second broods than during first broods, with differences of 0.06-0.07 RMR during incubation and of 0.32 RMR during nestling care. These differences correspond to the flying costs of females incubating eggs (0.09 RMR) and rearing nestlings (0.25 RMR). We conclude that nest placement in relation to microclimate can improve the female's energy budget, both in terms of the total daily expenditure and its diurnal pattern. From thermal considerations alone, delaying breeding into mid-summer would be advantageous, but this advantage is probably outweighed by the reduced chances for second and replacement clutches and by the necessity to complete moult before migration.
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The evolution of different parental care strategies is thought to result from variation in trade-offs between the costs and benefits associated with providing care. However, changing environmental conditions can alter such fitness trade-offs and favor plasticity in the type or amount of parental care provided. Avian incubation is a form of parental care where parents face changing environmental conditions, including variation in the risk of nest predation. Because parental activity can draw attention to the location of the nest, a reduction in nest visitation rates is a predicted response to an increased, immediate predation risk. Here, we experimentally increased the risk of nest predation using model presentations at nests of five coexisting species that differ in their ambient levels of nest predation. We examined whether individuals detect changes in nest predation risk and respond by reducing visitation to the nest. We also tested whether this behavioral response differs among species relative to differences in their ambient risk of nest predation. We found that males of all species detected the increased predation risk and reduced the rate at which they visited the nest to feed incubating females, and the magnitude of this change was highly correlated with differences in the risk of nest predation across species. Hence, as the vulnerability to nest predation increases, males appear more willing to trade the cost of reduced food delivery to the female against the benefit of reduced predation risk. Our results therefore suggest that nest predators can have differential effects on parental behaviors across species. We discuss how the comparative nature of our results can also provide insight into the evolution of behavioral plasticity. Copyright 2002.
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Ambient temperature is commonly thought to influence avian incubation behavior. However, results of empirical studies examining correlations between ambient temperature and bout duration are equivocal. We propose that these equivocal results can be partly explained by developing a conceptual understanding of how we should expect temperature to influence incubation. We demonstrate why linear correlation analyses across a wide range of temperatures can be inappropriate based on development of an incubation model for small birds that incorporates how ambient temperature influences both embryonic development and adult metabolism. We found support for predictions of the model using incubation data from orange-crowned warblers ( Vermivora celata ) in Arizona. Both off- and on-bout duration were positively correlated with ambient temperature between 9° and 26°C, but unrelated to ambient temperature <9° and 26-40°C. Bout durations declined as ambient temperature approached or exceeded 40°C. Incubating orange-crowned warblers appeared to avoid bouts off the nest <7 min and bouts on the nest <20 min. Time of day, duration of the previous bout, and variation among nests all explained variation in both on- and off-bout duration. Although we found support for the general shape of the incubation model, temperature still explained only a small portion of the overall variation in on- and off-bout duration. Results of previous studies were generally consistent with the model for off-bout duration; most studies in colder environments reported positive correlations with temperature, and the one negative correlation reported was from a hot environment. However, the relationships between on-bout duration and temperature reported in previous studies were less consistent with our model and our data. Although some discrepancies could be explained by considering our model, some studies reported negative correlations in cold environments. The effect of ambient temperature on duration of on-bouts probably differs among species based on the amount of fat reserves females typically carry during incubation and the extent of male incubation feeding. Additional studies of the effects of temperature on avian incubation will help improve the general model and ultimately aid our understanding of energetic and ecological constraints on avian incubation.
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Many species of birds line their nests with feathers, presumably because of the insulative qualities of feathers and because feathers may act as a barrier between nest parasites and nestlings. In 1993, we experimentally examined the role of feathers as nest insulation on the incubation behavior, nestling growth, and reproductive performance of Tree Swallows (Tachycineta bicolor) nesting in boxes in western Michigan. There were no significant differences between the incubation rhythms of females with experimental nests (i.e. no feathers) and females with control nests (i.e. with feathers). Nestlings that were reared in control nests had significantly longer right tarsi and right wing chords; their masses were significantly greater than nestlings reared in experimental nests. In addition, nested analyses of variance indicated that both female age class (i.e. second year, after second year, or after hatching year) and the brood within which a nestling was reared had significant effects on nestling growth until nestling day 12. Whether an individual nestling was infected with ectoparasites was independent of whether it was reared in an experimental or control nest. Nest insulation affected reproductive performance: females with experimental nests had significantly longer incubation periods and produced significantly fewer fledglings than did females with control nests. These results suggest that nest insulation may be an important factor influencing incubation behavior, nestling growth, and reproductive performance of Tree Swallows in western Michigan.
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The relationship between nest entrance orientation and latitude among ground-nesting passerines was reviewed using published information. Data were collated for seven North American and European species. Pooling within-species comparisons, there was a clear trend from a preference for north-facing nests at lower latitudes to eastward- or southward-facing nests farther north. Orientations differed significantly in eight of 12 cases for which statistical comparison was possible, means differing in the expected direction in six of these cases. These results highlight how the influence of solar radiation on nest microclimate typically delineates preferred nest orientation in these species, i.e., at lower latitudes, the need for shade results in a preference for northward orientations; at mid latitudes, eastward orientations predominate, reflecting a probable balance between the benefits of warmth in the early morning and shade in the afternoon; while at high latitudes, nests may be oriented southward to gain warmth throughout the day.
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We reviewed information on the demands of incubation to examine whether these could influence the optimal clutch size of birds. The results indicate that appreciable metabolic costs of incubation commonly exist, and that the incubation of enlarged clutches can impose penalties on birds. In 23 studies on 19 species, incubation metabolic rate (IMR) was not elevated above the metabolic rate of resting non-incubating birds (RMR), but contrary to the physiological predictions of King and others, IMR was greater than RMR in 15 studies on 15 species. Across species, IMR was substantially above basal metabolic rate (BMR), averaging 1.606 × BMR. Of six studies on three species performed under thermo-neutral conditions, none found IMR to be in excess of RMR. IMRs measured exclusively within the thermo-neutral zone averaged only 1.08 × BMR contrasting with the significantly higher figure of 1.72 × BMR under wider conditions. 16 of 17 studies on procellariiforms found IMR below RMR, indicating a significant difference between this and other orders. We could find no other taxonomic, or ecological factors which had clear effects on IMR. Where clutch size was adjusted experimentally during incubation, larger clutches were associated with: Significantly lower percentage hatching success in 11 of 19 studies; longer incubation periods in eight of ten studies; greater loss of adult body condition in two of five studies; and higher adult energy expenditure in eight of nine studies. Given that incubation does involve metabolic costs and given that the demands of incubation increase sufficiently with clutch size to affect breeding performance, we propose that the optimal clutch size of birds may in part by shaped by the number of eggs the parents can afford to incubate.
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Oxygen consumption in incubating starlings during the rewarming of a clutch was measured. The energy cost of rewarming the eggs increased with increasing length of the preceding inattentive periods and lower ambient temperature but not with clutch size. The contradiction between the measured costs of rewarming and those predicted from a heat-capacity model suggests a regulation of the blood flow in the brood patch independent of clutch size. Furthermore, a clutch size of six eggs seems to be optimal with respect to the cost of rewarming per egg. The question is raised of how much energy has to be produced exclusively for rewarming under natural conditions. It is suggested that, during inattentive periods (flight, foraging), energy is stored, and during rewarming it is channeled to the eggs. Consequently, no extra cost for rewarming may be necessary.
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Quantifying incubation patterns has often involved long observation periods in the field, video cameras, or the use of other electronic devices that sometimes require the partial destruction of clutches and insertion of artificial eggs. In this study, we used an inexpensive, nondestructive method involving temperature probes combined with data loggers to examine the incubation rhythm of female Black-throated Blue Warblers (Dendroica caerulescens). The method provided detailed records of on–off patterns for females for selected 24-h periods during incubation. Female warblers spent an average (±SE) of 64.0% of daylight hours incubating in bouts lasting 20.5 ± 1.5 min and made 2.4 ± 0.1 departures from the nest/h on trips that lasted 10.6 ± 0.7 min. Incubation bouts were longer and females spent more time incubating per hour in the mornings and late afternoons than at mid-day. Older females had longer incubation bouts and tended to have shorter incubation periods than did yearling females, suggesting that experienced individuals were more effective incubators. Because of its ease of use and because nests with probes were not depredated at a higher rate than controls, we suggest that the temperature probe/data logger method is an efficient and effective way to quantify incubation rhythms for open-cup nesting birds.
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In the pied flycatcher the female incubates alone. The incubation rhythm was studied at Aven, Ostfold (59°20'N) and Klaebu in S-Trondelag (63°15'N), Norway. In mid-June, daytime lasts c2 h longer at Klaebu. Females at Aven started the daily activity earlier in the morning both in terms of absolute time and relative to the sun, but there was no difference between the study areas with respect to daily inattentive time or daily number of periods-off. The incubation pattern varied significantly with air temperature; duration of periods-on decreased with increasing temperature, while the periods-off increased. However, the periods-on changed much more quickly than the periods-off, on the average by 0.8 min. per °C, compared to only 0.1 for periods-off. Attentiveness was therefore mainly regulated by variation in the duration of periods-on. Independently of air temperature, attentiveness also varied with the time of day. Findings support the hypothesis that the incubation rhythm is basically circadian with the photoperiod as a Zeitgeber, and with the air temperature as an important moderating factor. Mean constancy of incubation was 75.0% for 6 Klaebu-nests and 76.6% for 8 Aven-nests. -from Authors
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Only the female blue tit incubates and during that time is fed by the male. Just before and during the egg-laying period the female spends the night in the nest. The energy cost of incubation is relatively important below the lower critical temperature (c15oC). With a fall in the air temperature, energy expenditure increased in relation to that of the resting metabolism. The energy cost of incubation also increased with clutch size, by 6-7% for each additional egg. At air temperatures around 0oC (frequent in Fennoscandia) the female must increase her metabolic rate by 50-90% to keep the eggs in a normal-size clutch (10-13 eggs) warm. During the last days of incubation the metabolism of the embryos was accounted for; on the day before hatching this contributed c15% of the total oxygen consumption when the female was incubating a clutch of 13 eggs. -from Authors
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Recordings of temperature fluctuations in the nests of birds can be used to infer incubation behavior such as the frequency and duration of off-bouts. Until recently, collecting temperature recordings from a large number of nests was limited by the size and expense of data logger equipment. In this paper, we describe software we developed to help simplify the analysis of recordings of temperature or mass fluctuations over time. The software program, called Rhythm, works in conjunction with Raven, a bioacoustical analysis program, to partially automate the measurement of incubation off-bout duration and related statistics such as percent constancy. This novel application of Raven combined with advances in data logger technology facilitates investigation in several areas of ecological and behavioral research.
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We compared the incubation behaviour of 1-year-old female Savannah Sparrows Passerculus sandwichensis nesting for the first time with that of older females that had nested in previous years on Kent Island, New Brunswick, Canada. Using temperature probes inserted into 32 nests, we determined the length and variability of incubation shifts and recesses over 99 nest-days. At 14 of the nests, known-age females were matched, each pair consisting of an inexperienced yearling and an experienced older female, and nest temperatures were measured simultaneously. In addition, we quantified the duration of night-time incubation and the mean length and variation of more than 1350 incubation shifts and recesses as a function of female age, weather, time of day and date. In all respects, yearling and older females had equivalent incubation behaviour. The similarity between yearlings and older females suggests that fundamental aspects of incubation behaviour may be largely innate and unaffected by prior reproductive experience or other age-related variables.
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Two models were developed with the aim of predicting the optimal inattentive period (i.e time off the nest) of bird species in which only one sex of parent incubates the eggs. The models assumed that fitness was increased in individuals which maximized either total (TOTAL GAIN model) or net rate of metabolizable energy (NET RATE model) gained while foraging. Both models considered the energetic cost of reheating eggs cooled during inattentive periods. The models were evaluated in a study of incubation behaviour in female swallows Hirundo rustica (L.), by using laboratory data on egg cooling rates and field information on instantaneous mass changes while foraging (and hence energy gains). Both models predicted that inattentive periods longer than 5-6 mins would result in energy deficit and 84% of all observed inattentive periods were indeed shorter than 5-6 mins. The predicted optimal inattentive period (4-5 mins) was slightly longer than that most frequently observed (3-4 mins) when TOTAL GAIN was used and slightly shorter (2-3 mins predicted optimum) than the most frequent inattentive period class when using the predictions of NET RATE. The models are evaluated and possible non-energetic constraints on incubation behaviour are discussed.
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The feeding habits of an alpine passerine bird community was studied during the breeding season in the Pyrenees (Northeastern Spain). Five of the six species often fed on arthropods found on snow, and their use of this resource increased with elevation. Two high alpine birds, Montifringilla nivalis and Prunella collaris, mainly used snow patches. Two species that primarily forage at lower elevations, Oenanthe oenanthe and Anthus spinoletta, preferred alpine tundra despite the fact that all species had higher foraging rates (both per unit distance and unit time) on snow. High foraging rates on snowfields can be explained by greater prey detectability and accessibility. A smaller size and thus lower profitability of snow arthropods compared with those of alpine tundra may be the reason why alpine birds preferred snow patches only at the highest elevations, where arthropod abundance in other habitats is very low.
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Eggs of the parasitic Brown-headed Cowbird (Molothrus ater) often hatch before those of its hosts. I artificially incubated the eggs of the cowbird and the taxonomically related but nonparasitic Red-winged Blackbird (Agelaius phoeniceus) to determine if cowbird eggs have unique adaptations. To determine if cowbirds have a wider tolerance of acceptable incubation temperatures, the eggs from both species were incubated at 35, 38, and 40°C. Neither species' eggs hatched at 35 or 40°C, whereas 24 out of 42 cowbird eggs and 19 out of 36 redwing eggs hatched at 38°C. When corrected for differences in mass, cowbird and redwing eggs hatched 10 and 15%, sooner than expected, respectively, suggesting that cowbirds do not have an accelerated rate of embryonic development. Cowbirds may be adapted to lay smaller eggs that generally hatch sooner. Using values obtained from allometric equations that relate body mass and egg mass, cowbird and redwing eggs were 25 and 4% smaller, respectively, than expected. For cowbirds, there was no correlation between egg mass and length of incubation period, whereas there was a positive (but not significant) correlation for redwings. Additional cowbird eggs were incubated at 36 and 39°C to determine the effect on the length of the incubation period. The incubation periods of individual cowbird eggs ranged from 10.49 to 14.04 days at 39 and 36°C, respectively, whereas eggs incubated at 38°C had a mean incubation period of 11.61 days (n = 24), suggesting that cowbirds can tolerate some variation in incubation temperature and indicating a strong temperature effect. I found evidence that internal egg temperature varies with clutch composition. This may partially explain the variation in cowbird incubation periods and why cowbird eggs often hatch before host eggs.
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In 1975 and 1976, fallout (aerially dispersing arthropods trapped on snow) was collected from large permanent alpine snowfields on Mount Rainier (4392 m), Cascade Mountains. Spiders comprised 5.5% of all specimens collected, being fifth in abundance after Homoptera, Heteroptera, Hymenoptera, and Diptera. Overall, spider fallout density decreased steadily with elevation, probably reflecting a decrease of spider density in the atmosphere with altitude. Spiders from distant sources reached higher elevations. From April to October, spider fallout density (and thus spider dispersal in this area) showed a moderate peak in May/June, a minimum in September, and a high peak in October, similar to patterns known elsewhere. Only 5 of 23 spider species found in fallout were previously known as ballooners. Species ballooning as adults belonged to the families Araneidae, Theridiidae, Salticidae, and Thomisidae, not just Linyphiidae as previously reported. Analysis of probable origins of fallout species shows the importance of major landforms and weather patterns to success of spider aerial dispersal. Compared with embarkment and flight of ballooners, their immigration has been little studied; alpine fallout is an important potential source of such data.
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Experimentally changed clutch size did not affect hatching success in Blue Tits whereas the incubation period was longer for larger clutches.
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We studied incubation patterns and hatchability of Red-winged Blackbirds (Agelaius phoeniceus) nesting in two different wetland habitats--beaver ponds and sewage lagoons--in eastern Ontario during 1999-2001. We presumed that, if incubating Red-winged Blackbirds could acquire food more readily at sewage lagoons than at beaver ponds, they should respond by taking fewer and shorter foraging bouts, which would result in longer bouts of attentiveness, shorter incubation periods, and higher hatchability of eggs. Although differences were small, female foraging bouts were shorter and bouts of attentiveness were longer at sewage lagoons than they were at beaver ponds. Incubation constancies were subsequently greater, and, ultimately, incubation periods at sewage lagoons were shorter. Shorter incubation periods at sewage lagoons, however, did not result in increased hatchabi