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Parent birds face a tradeoff between spending time incubating their eggs and foraging. The duration and frequency of breaks taken by incubating parents are potentially influenced by the ambient temperature, which affects both egg cooling rate and parental metabolism. We used remote temperature data loggers to obtain an extensive, continuous sample...
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... least six eggs, or after the female stopped laying additional eggs if the final clutch had fewer than six eggs. To record ambient temperature, we attached one iButton to the bottom of each box on the outside, using sticky-backed Velcro. To monitor the female's presence, we placed a second iButton on the inside of the box in the nest with the eggs (Fig. 1). We did this by inserting the iButton into the tip of a black jersey gardening glove, which made it less visually obvious inside the dark nest box. We then wrapped the covered iButton in thin wire, threaded the wire through the nest and out a hole in the bottom of the nest box, and wrapped the wire around a screw on the outside of the ...
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In September 2003 and November 2004 in the Lobos de Afuera Islands (06°56’40”S / 80°43’24”W, Peru) I evaluated the parental care of two pairs of Nazca Boobies (Sula granti). Observations were conducted for 144 daytime hours per nest. As in other reproductive areas of the species, the largest number of feeding events were conducted by the females, w...
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... The negative relationship between nest attendance and mean ambient temperature (range: 10.0-22.9 ֯ C) indicated that on warmer days Kentish Plovers could afford to spend more time off the nest, presumably due to slower cooling of the exposed eggs (Walters et al. 2016). Interestingly, the significant interaction term between time of day and ambient temperature revealed that during the night, nest attendance was always high and very constant, while during the day nest attendance varied greatly as a result of ambient temperature (Figure 1). ...
... Temperatures in nest bowls (N = 42) just beside the eggs were recorded using iButtons to detect the timing and length of incubation recesses. The iButtons were fastened to a wire, which was threaded through the nest material and secured to the wooden bottom of the nest box to prevent females from moving them (Johnson et al., 2013a;Walters et al., 2016;Stalwick & Wiebe, 2019a). Direct observations of some incubating females in a previous study confirmed that absences from the nest corresponded well with traces recorded by iButtons (Stalwick & Wiebe, 2019a). ...
... Direct observations of some incubating females in a previous study confirmed that absences from the nest corresponded well with traces recorded by iButtons (Stalwick & Wiebe, 2019a). The ambient temperature was recorded during the same time using a separate iButton attached to the outside bottom of nest boxes (see Walters et al., 2016). When multiple nest boxes were located within about 5 km of each other and predator trials at the boxes occurred on the same day, a single ambient temperature reading was used for all the boxes. ...
... We identified the beginning of a recess (off-bout) as any time the temperature dropped by at least 1.5°C over a 3-min period, and the end of a recess was similarly marked when the temperature increased by least 1.5°C over a 3-min period (Walters et al., 2016). For each of the four time periods (pre-trial (control), and the three post-trial), we calculated the percentage of daylight hours spent on the nest (incubation constancy), the average recess length (minutes), and the recess rate (number/hour). ...
Parent birds may alter incubation rhythms in response to predation risk but few studies have examined the recovery time immediately after exposure to a predator. Here, we examined incubation rhythms in mountain bluebirds ( Sialia currucoides ) in response to a simulated nest predator, a taxidermy-mounted squirrel. We used data loggers (iButtons) to measure the recess (off-bout) length, recess rate, and constancy of incubation and found no relationship between incubation rhythms and female age, body size and aggressiveness. Incubating females reacted to the predator by reducing nest visitation rates and increasing recess length but did not change incubation constancy. Instead, constancy was negatively associated with ambient temperature. Changes in incubation behaviour lasted about 48 h before returning to pre-exposure patterns. Our results suggest that modifying incubation rhythms is costly for female birds and the demand to regulate egg temperature efficiently limits the length of behavioural responses to the threat of nest predation.
... Higher nest temperatures can reduce the time needed for incubation or brooding the nestlings (Mueller et al. 2019). Therefore, adults could potentially increase the number and duration of foraging trips as a response to higher nest temperatures (Rauter et al. 2002, Walters et al. 2016). This might not only lead to higher provisioning rates but also increase the time spent for self-maintenance. ...
Timing and location of reproduction are central to reproductive success across taxa. Among birds, many species have evolved specific strategies to cope with environmental variability including shifts in timing of reproduction to track resource availability or selecting suitable nest location. In mountain ecosystems, complex topography and pronounced seasonality result in particularly high spatiotemporal variability of environmental conditions. Moreover, the risk of climate‐induced resource mismatches is particularly acute in mountain regions given that temperature is increasing more rapidly than in the lowlands. We investigated how a high‐elevation passerine, the white‐winged snowfinch Montifringilla nivalis, selects its nest site in relation to nest cavity characteristics, habitat composition and snow condition. We used a combination of field habitat mapping and satellite remote sensing to compare occupied nest sites with randomly selected pseudo‐absence sites. In the first half of the breeding season, snowfinches preferred nest cavities oriented towards the morning sun while they used cavities proportional to their availability later on. This preference might relate to the nest microclimate offering eco‐physiological advantages, namely thermoregulatory benefits for incubating adults and nestlings under the harsh conditions typically encountered in the alpine environment. Nest sites were consistently located in areas with greater‐than‐average snow cover at hatching date, likely mirroring the foraging preferences for tipulid larvae developing in meltwater along snowfields. Due to the particularly rapid climate shifts typical of mountain ecosystems, spatiotemporal mismatches between foraging grounds and nest sites are expected in the future. This may negatively influence demographic trajectories of the white‐winged snowfinch. The installation of well‐designed nest boxes in optimal habitat configurations could to some extent help mitigate this risk.
... found in the American robin (Turdus migratorius; Ospina et al., 2018). During the time that females leave their nests unattended, nest cooling is expected to depend on the difference between the nest and the environmental temperature, as described for the Carolina chickadees (Poecile carolinensis; Walters et al., 2016). In the clay-colored thrush, in the absence of incubating females, nest walls have little influence in reducing cooling, and the isolation is mainly provided by the base of the nest which is built with adobe, as in the common blackbird (Turdus merula) and the song thrush (T. ...
The internal temperature of nests largely depends on the materials used in their construction because the characteristics of each material affect the isolation of nest walls. In urban environments, the availability of natural materials for nest building decreases, while the availability of artificial materials increases. Therefore, many urban bird species use more artificial materials for nest building inside cities, which may affect the thermal properties of the nest. We conducted an experiment to measure the effect of artificial materials included as part of the nest structure, on nest thermoregulation. We used as a model, nests of the clay-colored thrush (Turdus grayi), an urban bird species that have been reported using artificial nest materials. In our experiment, we measured how variation in artificial materials mass affects the nest cooling rate in a climate-controlled room. We found that artificial materials increased the cooling rate of clay-colored thrush nests, compared with nests with only natural materials. This result is especially relevant because showed a negative direct effect of the use of artificial material for nest building in birds. Considering that the availability of artificial material is increasing in urban areas, while natural material is decreasing, it is expected that the negative effect of using artificital material for nest construction would increase in the clay-colored thrush and other city bird species.
... Despite the reproductive benefits of increasing incubation effort, females might prioritize self-maintenance (e.g. preening, foraging or avoidance of nest predators) at increasing ambient temperatures, by having longer (Walters et al. 2016, Capp et al. 2018 or more frequent off-bouts (MacDonald et al. 2014). Either investing in incubation or self-maintenance time is not species-specific but population dependent, since both behavioural responses have been reported within the same species (e.g. ...
... Energetic needs push to shorter bouts early and late in the day, reaching a maximum by midday (Conway and Martin 2000a). However the opposite relationship, with minimum bout duration around midday, has been also reported Martin 2009, Kovařík et al. 2009), and some studies have even found a linear decrease of nest attentiveness throughout the day (Walters et al. 2016, Bambini et al. 2019). On the other hand, embryo development entails increasing egg-cooling rates, causing a linear decrease of bout duration along the incubation period (Cooper and Voss 2013). ...
... As incubation progresses, females may shorten off-bouts (Walters et al. 2016, Schöll et al. 2019 or both on-and offbouts Martin 2009, Cooper andVoss 2013) to meet embryo energetic needs (Cooper and Voss 2013). It usually translates into higher daily nest attentiveness (Bueno-Enciso et al. 2017, Simmonds et al. 2017, Bambini et al. 2019) but many studies have failed to detect any effect at all (Conway and Martin 2000a, Álvarez and Barba 2014, Capp et al. 2018 even after observing shorter bouts Martin 2009, MacDonald et al. 2014). ...
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.
... Indeed, parents also alter incubation behavior in relation to time of day, time in the season, embryo age, ambient temperature and precipitation (Feldheim, 1997;Álvarez and Barba, 2014;McClintock et al., 2014;Walters et al., 2016;Carroll et al., 2018). Parental behavior is integral to mitigating the effects of weather at the nest, especially extreme weather events, such as heavy rain, flooding or abnormal temperatures (Burger, 1978;Clauser and McRae, 2017). ...
Avian nests are critical for successful reproduction in birds. Nest microclimate can affect egg development, chick growth and fledgling success, suggesting that nest building behavior should be under strong selective pressure to nesting conditions. Given that the internal microclimate of the nest is critical for avian fitness, it is expected that nest morphology is shaped by the local environment. Here we review the relationship between nest morphology and climate across species’ distributions. We collate growing evidence that supports a link between environmental conditions and particular nest traits, within species and across species. We discuss the degree to which phenotypic plasticity in nesting behavior can contribute to observed variation in nest traits, the role of phylogenetic history in determining nest morphology, and which nest traits are likely to be influenced by climatic conditions. Finally, we identify gaps in our understanding of the evolution of nest morphology and suggest topics for future research. Overall, we argue that nests are part of the extended phenotype of a bird, they play a crucial role in their reproductive success, and may be an important factor in determining which species will be able to persist in the face of ongoing climate change.
... A likely mechanism for higher temperatures increasing the duration of the incubation period is adjustment of incubation behavior under different ambient temperatures. For example, incubating females may leave the nest for shorter periods in cold conditions (Voss et al., 2006;Amininasab et al., 2016;Walters et al., 2016), so eggs remain within the optimal incubation temperature range for a greater proportion of the day. However, other studies have reported greater nest attendance when ambient temperatures are higher (Morton and Pereyra, 1985;Ardia et al., 2010;MacDonald et al., 2013;Simmonds et al., 2017), perhaps because lower costs of heating eggs and/or foraging allow females to incubate for longer before they need to forage again. ...
The timing of breeding often has a profound influence on the reproductive success of birds living in seasonal environments with rapidly changing nestling food availability. Timing is typically investigated with reference to lay dates, but it is the time of hatching that determines the ambient conditions and food availability that nestlings experience. Thus, in addition to lay date, phenological studies may also have to take account of variation in the length of the incubation period, which is likely to depend on both environmental conditions and parental traits. The primary aim of this study was to use a 24-year dataset to investigate the abiotic and biotic factors influencing variation in incubation duration in long-tailed tits (Aegithalos caudatus), a species in which incubation duration varies substantially (range: 12–26 days). We found support for our predictions that drier conditions, later breeding attempts and larger clutches were associated with shorter incubation periods. Larger clutches were also more resilient to increases in incubation duration associated with wet conditions. Surprisingly, warmer ambient conditions were associated with longer incubation periods. Secondly, we assessed the consequences of variation in the length of incubation periods for the risk of nest predation and the hatching success of surviving clutches. We show that longer incubation periods are likely to be costly due to increased exposure to nest predators. In contrast, we found only marginal effects of environmental conditions or incubation duration on hatching success, implying that wet conditions cause slower embryo growth and hence longer incubation periods, rather than causing embryo fatality. We suggest that long-tailed tits’ nests and parental behavior protect eggs from mortality arising directly from adverse weather conditions.
... As several studies have demonstrated the importance of ambient temperature on avian incubation behaviour (e.g. Conway and Martin 2000;McClintock et al. 2014;Walters et al. 2016), we also used measurements from the nearest weather station (Kalmar) of the Swedish Meteorological and Hydrological Institute, from 2014 (downloaded at https:// opendata-download-metobs.smhi.se/explore/#) as a covariate in our models (see below). ...
Food availability sets the stage for incubation behaviour of a female bird and thereby indirectly determines the nest temperature, which in turn affects development and metabolism of avian embryos. Changes in development and metabolism in turn are known to influence offspring's ability to adjust to environmental changes later in life. However, few studies have investigated the role of interspecific differences in incubation behaviour in relation to niche separation between competing sibling species. We studied the effects of habitat quality (in terms of caterpillar availability) on incubation behaviour of two ecologically similar and closely related species, collared and pied flycatchers (Ficedula albicollis and F. hypoleuca), in their hybrid zone on the island of Öland, Sweden. Even though both species prefer caterpillar-rich deciduous forests as nesting sites, collared flycatchers, whose nestlings have higher energetic demands, are able to nest only in deciduous forests, whereas pied flycatchers have more flexible habitat requirements. Overall, higher food availability was associated with increased nest attendance, higher incubation temperature and a lower number of foraging trips across species. In addition, collared flycatchers had more frequent and shorter foraging trips across habitat types, allocated more heat to eggs and therefore maintained higher nest temperatures compared to pied flycatchers. We argue that the higher heat allocation or the need to maintain a higher nest temperature for embryo development may constrain collared flycatchers to focus on relatively more profitable prey. Our results highlight the importance of considering incubation behaviour in the context of understanding species differences in niche use.
Significance statement:
Niche separation plays an important role in mitigating effects of competition between closely related species. Whether species differences in incubation behaviour relate to differences in niche use remains unknown. We compared incubation behaviour of two sympatric flycatcher species that differ in sensitivity to food availability. The competitively more dominant and larger species, the collared flycatcher, whose nestlings are more sensitive to food shortages, made more frequent foraging trips but allocated more heat to eggs, leading to higher nest temperature despite lower nest attendance, compared to pied flycatchers. These interspecific differences may be a result of differences in embryo sensitivity or female physiology and contribute to the niche separation between the species, which in turn can facilitate coexistence.
... Why unsuccessful birds in this study were more likely to respond specifically by putting more pieces into their nest in Experiment 2 is not clear. One possibility may be that birds are able to monitor their nest temperature (e.g., Álvarez and Barba 2014;Walters et al. 2016). If so, then it seems plausible that builders can associate the nest temperature with reproductive outcome (just as they can associate nest color with reproductive outcome: Muth and Healy 2011). ...
There are numerous observational studies on intraspecific variation in avian nest building and a single experimental manipulation. The general consensus is that birds build nests in response to environmental conditions, but it is not clear whether such flexibility in nest building is reproductively advantageous. To test the relationship between building flexibility and reproductive success, we allowed captive zebra finches to build their first nest, using string, and to breed in temperature-controlled rooms held at 14 or 30 °C. Once the offspring had fledged, we returned half the pairs to breed at the same temperature while half the pairs were switched to the alternative temperature. We provided all pairs with string and left them to build and breed a second time. For their first nest, pairs that built at 14 °C used more string than did pairs that built at 30 °C, and pairs that bred successfully built a nest with more string than did unsuccessful pairs. When pairs built their second nest, however, temperature no longer explained the number of pieces of string they used; rather, irrespective of the ambient temperature, pairs that had successfully produced young from their first nest used the same amount of string for their second nest, whereas those that had failed to reproduce with their first nest used more string. These latter pairs were then more likely to repro- duce successfully. Ambient temperature, therefore, did affect the nest the pairs built but only in the absence of reproductive experience.
... Birds can adjust the amount of time they spend on (on-bout) and off (off-bout) a nest and the frequency at which they take off-bouts. For example, in heated nestboxes female great tits and Carolina chickadees (Poecile carolinensis) take longer off-bouts during incubation and are able to maintain a suitable nest temperature (Álvarez and Barba, 2014;Walters et al., 2016). In an environment where temperature may fluctuate day by day, by as much as 10°C (Chapter 4) it may be more efficient to adjust incubation behaviour. ...
Nest building is an important reproductive behaviour which has received little attention. In this thesis I address two key questions which have been overlooked: 1) What causes intraspecific variation in nest structure? and 2) What are the neural mechanisms of nest building? Using a wild population of blue tits (Cyanistes caeruleus) building in nestboxes in St Andrews, I found that female blue tits advanced their nest initiation in warmer years, and constructed lighter nests when April was warmer, but they did not change the amount of specific materials with which they built their nest. Advancing breeding events also did not affect female adult survival in my population. However, when comparing material metrics and temperature over specific time periods I found a number of relationships between temperature and the mass and proportion of materials in a nest e.g. insulatory material mass decreased as minimum temperature during building increased. In a laboratory experiment, I found that at cooler temperatures zebra finches (Taeniopygia guttata) constructed heavier nests using more pieces of string. When these birds built their second nest, however (either at the same or a different temperature), pairs that had previously reproduced successfully used the same number of pieces of string to build their nest while previously unsuccessful pairs increased the number of pieces of string used, regardless of temperature. With regard to the neural underpinnings of nest building, I found that hypothalamic vasotocin mRNA expression (a nonapeptide hormone primarily responsible for social behaviour) was higher in male zebra finch builders than in non-builders two hours after the start of nest building. Furthermore, I identified areas of the anterior motor pathway, social behaviour network and cerebellum that are active during nest construction. In this thesis, I have identified individual plasticity in nest building in response to temperature, and some of the neural underpinnings of the social behaviours involved in nest building.
