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Seasonal changes in the total active period (time between emergence from the roost and entering the roost again) for male (blue) and female (red) Blue Tits. The left panel shows data between October and 31 March ('non-breeding', months indicated by letters); the right panel shows the data from 21 days before the focal female's first egg (day 0) until July ('breeding'). Shown are smoothed values as calculated by the GAMM (solid line; see Methods) and the 95% confidence intervals (dashed lines). The black solid line shows day length (i.e. the time between sunrise and sunset). The right panel shows the data from 21 days before the focal female's first egg (day 0) until July. The approximate breeding stage is shown above the right panel (Nest building, Egg-laying, Incubation, Nestling period, Post-breeding).
Source publication
All birds sleep and many do so in a specific location, the roost. Thus, every day each individual needs to decide when to go to (enter) and leave the roosting place. This determines the timing of activity, a trait shaped by both natural and sexual selection. Despite its importance in a variety of contexts, including foraging, predation, mating succ...
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Context 1
... of activity is shown in Figure 2. Overall, in both sexes, individuals usually entered the roost before sunset, except during mid-winter when the days are shortest. In winter, individuals were therefore active for a much shorter period than in summer (Fig. 3). During the breeding season, individuals changed their timing around the start of laying: both sexes entered the nestbox progressively earlier in the evening, but the pattern was most pronounced in females during the incubation Table ...
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Sexual selection theory provides a framework for investigating the evolution of traits involved in attracting and competing for mates. Given the sexual function of such traits, studies generally focus on individual interactions (i.e., displays and contests) in explaining trait origin and persistence. We show that ecological factors can strongly inf...
Citations
... Variation in the timing of activity has been widely reported both within-and among-individuals from the same population [1][2][3][4]. For example, withinindividuals, timing of activity (e.g. ...
... For example, withinindividuals, timing of activity (e.g. wakefulness, movement and foraging) often varies with ambient temperature [3,[5][6][7], season [1,5,6], daylength [7,8], predation risk [9,10] and weather conditions [5,8]. In songbirds, daylength and ambient temperature are important extrinsic factors that shape the timing of activity; shorter days and colder temperatures generally result in shorter active periods [3,8]. ...
... wakefulness, movement and foraging) often varies with ambient temperature [3,[5][6][7], season [1,5,6], daylength [7,8], predation risk [9,10] and weather conditions [5,8]. In songbirds, daylength and ambient temperature are important extrinsic factors that shape the timing of activity; shorter days and colder temperatures generally result in shorter active periods [3,8]. Consistent among-individual differences in the timing of activity have also been reported [11]. ...
The timing and amount of foraging in birds are shaped by many of the same extrinsic factors, including temperature and daylength, as well as intrinsic factors, such as sex and age. Here, we investigate co-variation between these traits. We observed a population of 143 individually marked black-capped chickadees (Poecile atricapillus) over a 90 day period during the winter. For each day, we recorded the time an individual began and ended feeder use relative to sunrise/sunset, and the total number of feeder visits. Within-individuals, both earlier first feeder visit and later last feeder visit were associated with higher total daily feeder visits but lower feeding rates. Individuals also differed consistently in the timing of first and last feeder visits, and individuals that consistently started feeder use earlier in the day ended feeder use later and had higher total daily feeder visits compared with those that started later, but had no difference in feeding rate. Our study demonstrates that variation in the timing of foraging can have important consequences for energy acquisition at both the within- and among-individual levels.
... Most studies have only examined the influence of ALAN and noise pollution on daily rhythms of male songbirds (e.g., [4,6,23,24,26,27,29,[32][33][34][36][37][38][39]), while fewer studies have looked at their influence on daily rhythms of female songbirds (but see [7,31,[44][45][46][47]). As sex-specific differences in activity patterns have been found in several songbird species [45][46][47], males and females may be affected differently when being exposed to ALAN or noise pollution, especially during the breeding season (e.g., [41]). ...
... Most studies have only examined the influence of ALAN and noise pollution on daily rhythms of male songbirds (e.g., [4,6,23,24,26,27,29,[32][33][34][36][37][38][39]), while fewer studies have looked at their influence on daily rhythms of female songbirds (but see [7,31,[44][45][46][47]). As sex-specific differences in activity patterns have been found in several songbird species [45][46][47], males and females may be affected differently when being exposed to ALAN or noise pollution, especially during the breeding season (e.g., [41]). ...
... Besides the onset of male dawn song and female emergence time, the onset of female calling behaviour was used as a proxy for the activity onset of the female. Covariables that could potentially have influenced activity onset, such as ambient temperature [4,45,54,55], precipitation [45] and the stage of the egg-laying phase [45][46][47]52], were also taken into account. Using this approach, we not only investigated direct effects of anthropogenic stressors on male and female great tits but also potential indirect effects on females that were transmitted by the male via vocal communication. ...
Artificial light at night (ALAN) and noise pollution are two important stressors associated with urbanisation that can have a profound impact on animal behaviour and physiology, potentially disrupting biological rhythms. Although the influence of ALAN and noise pollution on daily activity patterns of songbirds has been clearly demonstrated, studies often focus on males, and the few that examined females have not included the potential influence of males on female activity patterns. Using free-living pairs of great tits (Parus major) as a model, we examined for the first time the effects of ALAN and noise pollution and their interaction on the onset of (vocal) activity in both members of a pair. We focused on the egg-laying phase, when both sexes are most vocally active. The onset of male dawn song, female emergence time from the nest box and the onset of female calling in the nest box were measured and used as a proxy for the chronotype. The repeatabilities for all chronotype proxies were high, with higher repeatabilities for males. Consistent with previous studies, ALAN advanced the onset of male dawn song, while it did not elicit a strong response in female emergence time. Additionally, our results suggest an indirect effect of ALAN on the onset of female vocal activity via acoustic interaction with the male. Noise pollution advanced the emergence time in females, while an interaction between ALAN and noise pollution was found for the onset of female calling. In agreement with previous studies, several covariables were shown to have an influence on the activity onset. Taking several proxies for chronotype into account, this study has provided robust evidence of effects of ALAN on male and female cavity-nesting songbirds during the egg-laying period.
... This observation that birds held on LDs did not begin their daily activity earlier relative to lights on than when they were unimplanted and held on short-days may be due to potential physiological limitations in the maximum total duration they are capable of being active per day. An observational study performed in blue tits showed that birds used a smaller proportion of available daylight during summer months (i.e., waking later to relative sunrise and ending activity earlier relative to sunset) even though birds were more active in the total number of hours compared to winter months (Schlicht and Kempenaers 2020). In a study of arctic songbirds-it was observed that Lapland longspurs (Calcarius lapponicus) have a period of quiescent, even though there was available daylight (Ashley et al. 2013). ...
... In a study of arctic songbirds-it was observed that Lapland longspurs (Calcarius lapponicus) have a period of quiescent, even though there was available daylight (Ashley et al. 2013). Additionally, while the shift in chronotype to earlier is observed leading up to and the beginning part of the breeding season, in temperate breeding birds, the onset of activity steadily becomes later after sunrise as photoperiod approaches its annual maximum (Maury, Serota, and Williams 2020;Schlicht and Kempenaers 2020). These observation suggest a physical limitation to the number of active hours individuals can sustain under longer daylengths; our manipulations of 16L:8D approximates the natural summer maximum of Fargo. ...
Seasonal changes in sleep/wake cycles and behaviors related to reproduction often co‐occur with seasonal fluctuations in sex hormones. Experimental studies have established that fluctuations in circulating testosterone mediate circadian rhythms. However, most studies are performed under constant lighting conditions and fail to investigate the effects of testosterone on the phenotypic output of circadian rhythms, that is, chronotype (daily activity patterns under light:dark cycles). Here, we experimentally elevated testosterone with implants during short nonbreeding daylengths in male house sparrows ( Passer domesticus ) to test if observed seasonal changes in chronotype are directly in response to photoperiod or to testosterone. We fitted individuals with accelerometers to track activity across treatment periods. Birds experienced three treatments periods: short day photoperiods before manipulation (SD), followed by testosterone implants while still on short days (SD + T). Implants were then removed. After a decrease in cloacal protuberance size, an indicator of low testosterone levels, birds were then photostimulated on long days (LD). Blood samples were collected at night, when testosterone peaks, to compare testosterone levels to daily onset/offset activity for experimental periods. Our results indicate that experimentally elevated testosterone under short nonbreeding photoperiods significantly advanced daily onset of activity and total daily activity relative to daylength. This suggests that testosterone, independent of photoperiod, is responsible for seasonal shifts in chronotypes and daily activity rhythms. These findings suggest that sex steroid hormone actions regulate timing of daily behaviors, likely coordinating expression of reproductive behaviors to appropriate times of the day.
... weather conditions (Schlicht & Kempenaers, 2020) or conspecifics (Favreau et al., 2009 have not been studied yet (but see Steinmeyer et al., 2013). 98 99 ...
... In response to the weather conditions, we found a delayed onset of nest visits in response to an 378 increased amount of rain at night. This was similar to what has been previously found in blue tits 379 (Schlicht & Kempenaers, 2020), though we did not find a response to daytime rain in offset. As a 380 rainy night is likely associated with a rainy morning, those conditions might be unsuitable for foraging 381 or chick provisioning. ...
... conditions (Lejeune et al., 2019;Radford et al., 2001). In response to ambient temperature, we found 383 no significant shift in onset as previously shown for great tits (Lehmann et al., 2012;Stuber et al., 384 2015) but contrasting to an advance seen in blue tits (Schlicht & Kempenaers, 2020 inside the breeding nest-box (Kluijver, 1950). Therefore, the nest visits likely represent activity 392 ...
Diel rhythms are driven by genetic and environmental components. These rhythms are mediated by the circadian clock, and entail rhythmicity of various physiological and behavioural traits. Although individuals show to some extent repeatable timing (i.e., chronotype), there is ample variation of diel timing observed within and between individuals of the same species. Here, we investigated various environmental factors, including timing of the social partner, that could explain day-to-day variation within individuals. Synchronisation with the social partner during provisioning timing could increase breeding success, and decrease extrapair paternity opportunities for females during the fertile period in case of consistent timing across the breeding stages. Therefore, we also investigated fitness consequences of between-individual variation. We first assessed the magnitude of between- and within-individual variation in the timing of nest visits by great tits ( Parus major ). We monitored nest visits of males and females in 37 broods during chick provisioning in 2020 and 2021. Next, we explored the responsiveness of the diel timing to environmental variables, specifically comparing abiotic and social factors. The onset of nest visits varied significantly with day within the breeding season, rainfall and the diel timing of the breeding partner but not with night temperature. In response to the partner’s onset, females responded stronger compared to males. By contrast, offset was generally more variable within individuals and less variation was explained by the environmental variables. Both males and females delayed their activity offset with the progressing season and females also had a later onset with more daytime rainfall. Further, the reproductive output and extrapair paternity were independent of parental chronotype and their synchronisation within pairs. It is possible that consistency of chronotypes is less important for reproductive success than the ability to plastically respond to changing environmental conditions. Thus, the next step could be to investigate potential individual differences in plasticity which could be even linked to specific chronotypes. This information might be crucial to predict how species can cope with unpredictable environmental conditions.
... Consistency in the timing of activities is typically referred to as an individual's chronotype. Although an increasing number of studies have demonstrated the existence of chronotypes in multiple species (Al os et al., 2017a;Chmura et al., 2020;Dominoni, 2013;Graham et al., 2017;Grunst et al., 2021;Maury et al., 2020;Schlicht & Kempenaers, 2020;Steinmeyer et al., 2010;Stuber et al., 2015), its adaptive significance and how this variation is maintained in the population remain largely unknown. ...
... Sex steroids may also affect aggression, although the exact mechanisms underlying this relationship are still not fully understood (Hau et al., 2000;Heimovics et al., 2015Heimovics et al., , 2018Quintana et al., 2021;Soma, 2006;Soma et al., 2008). Further, in the run-up to the breeding season, a period with great changes in sex steroid concentrations for both males and females, males tend to start activity progressively earlier in the morning than females (Schlicht & Kempenaers, 2020;Stuber et al., 2015), which may suggest that chronotype is regulated by sex hormones in male great tits too. ...
Individual variation in the timing of activities is increasingly being reported for a wide variety of species, often measured as the timing of activity onset in the morning. However, so far, the adaptive significance of consistent variation in temporal phenotypes (i.e. the chronotype) remains largely elusive. Potentially, differences in timing of activities may arise as a result of competition among individuals for resources. Less aggressive individuals may try to avoid competition by becoming active earlier during the day when other individuals are still inactive, leading to a positive correlation between chronotype and aggressive personality type (i.e. a behavioural syndrome). To investigate this, we assessed the chronotype of female great tits, Parus major, by measuring emergence time from the nestbox in the morning and experimentally tested their levels of same-sex aggression through simulated territorial intrusion tests. Contradicting our initial hypothesis, consistently more aggressive females became active earlier during the day compared to less aggressive females, which could be caused by shared underlying mechanisms, like pleiotropic effects of sex hormones or gene pleiotropy, which potentially impose constraints on the independent evolution of both traits. Surprisingly, on the within-individual level we found an opposing correlation between emergence time and aggression. Our findings highlight the need for further investigations into the interplay between chronotype and aggression that take the underlying mechanisms into account in order to understand the adaptive significance of this trait association.
... For this, we assessed activity patterns of female great tits during incubation from nest temperature data. Incubating females adjust activity timing depending on incubation stage and environmental factors leading to differences between days (McGlade et al., 2023;Schlicht & Kempenaers, 2020). In particular, they delay their activity onset and advance their offset throughout incubation, while responses to environmental factors, such as temperature and rain fall, additionally increase variation between days. ...
... In particular, they delay their activity onset and advance their offset throughout incubation, while responses to environmental factors, such as temperature and rain fall, additionally increase variation between days. This large plasticity in females is also reflected in their repeatability of onsets ranging from 0.13 to 0.46 and offsets from 0.00 to 0.37 (Meijdam et al., 2022;Schlicht & Kempenaers, 2020;Stuber et al., 2015). It is important to experimentally disentangle daily effects from those of ALAN by looking at between-as well as within-individual responses. ...
... Behavioral responses towards ALAN in the wild might be relatively weak due to factors other than natural and artificial light influencing activity patterns. For example, weather conditions have been shown to alter incubation activity patterns (Coe et al., 2015) as well as activity onset and offset throughout the year (Schlicht & Kempenaers, 2020). Our study population is located on an island in the North Sea and was, therefore, particularly exposed to the wet weather condition in May 2021, leading to many laying and incubation delays as well as desertions during incubation and chick provisioning (own observations). ...
Artificial light at night (ALAN) widely affects wildlife by blurring light‐dark differences, including transitions such as sunrise and sunset, thereby affecting regulation of diel rhythms. As a result, activity onsets in many wild diurnal songbirds advance under ALAN. From chronobiological studies, it is known that the direction and strength of the response to light depends on when during the night exposure takes place. However, these experiments are mostly done under continuous light conditions, when animals have free‐running rhythms. It remains unclear whether phase‐dependence also holds in entrained, wild songbirds; i.e., does the effect of ALAN on activity patterns differ between exposure in the morning compared to the evening? This information is essential to assess the effects of mitigation measures by limiting ALAN to selected times of the night. We exposed incubating great tits ( Parus major ) inside the nest‐box to 4 h of dim light, of which 1 h overlapped with dawn before sunrise or dusk after sunset. We found a small advancing effect of morning‐light on activity onset and of evening‐light on offset compared to dark controls but not vice versa . Breeding success and chick condition were unaffected by the light treatments. However, light‐treated females had lower weights 9–18 days after the end of the treatment compared to the controls, independent of whether ALAN occurred in the morning or the evening, indicating possible costs of ALAN. Despite the weak behavioral response, ALAN might have affected the females' circadian clock or physiology resulting in lower body condition.
... Some authors have suggested that the R scores of circadian-related behaviours fluctuate across the reproductive period (Chmura et al., 2020;Maury et al., 2020;Schlicht & Kempenaers, 2020), but only Schlicht and Kempenaers (2020) compared the estimates of R in blue tits, Cyanistes caeruleus, for the nonbreeding and breeding periods. In contrast to our results, they found that the R for both sexes was lower during the breading period than in the nonbreeding period. ...
... The behavioural responses of female blue tits are more dependent on environmental conditions, which may explain why they are more consistent in their behaviour in the nonbreeding period. For example, during incubation and in the first days of nestling rearing, since nestlings do not thermoregulate, awakening time is strongly influenced by temperature (Schlicht & Kempenaers, 2020). In the morning, females leave the nest when temperatures are high enough not to compromise nestling survival and then extend their activity depending on their daily needs. ...
... Our results for the effect of temperature on behaviour during the prespawning period are consistent with findings in birds and nonhuman mammals (e.g. Chmura et al., 2020), where warm temperatures increased activity durations, likely due to increased foraging success and reduced energy costs (Schlicht & Kempenaers, 2020;Stuber et al., 2015). However, in fish, an increase in temperature leads to an increase in metabolic rate and, therefore, energetic requirements (see Johansen et al., 2015). ...
... Blue tits exhibit a pronounced dawn chorus and a less pronounced dusk chorus [9][10][11][12][13]. In the early breeding season males on average wake up and start their activity earlier in the morning than females, and females go to roost earlier than males in the evening [14,15], implying that criterion 1 is met in blue tits. To evaluate whether male blue tits sing more when their female is absent (criterion 2), we defined the 'absence' of the female as the time she spent alone inside a nest-box, and compared male song rate during this period with periods of equal length before the female entered the nest-box and after she left the nestbox. ...
... R. Soc. B 290: 20232266 a median clutch size of 10 eggs (range [4][5][6][7][8][9][10][11][12][13][14][15][16]. In blue tits, the female builds the nest and incubates alone, but the male may provide her with food [16,17]. ...
... We programmed the sound recorders so that they recorded continuously each day from 2 h before sunrise to 30 min after sunset. During the study period (days −5 to +5 relative to the start of egg laying, day 0), males left their roosting site on average more than 20 min earlier in the morning and entered it about 10 min later in the evening than females (data re-analysed from [15]). From the recordings, we extracted all song (sonograms shown in electronic supplementary material, figure S4) during the following periods: (1) one hour around sunrise (30 min before and 30 min after), (2) 20 min around sunset (10 min before and 10 min after), (3) during the day, whenever the focal female was inside the nest-box (for at least 2.5 min), and during the corresponding periods of the same duration (as her stay inside) before she entered and after she left the nest-box (see figure 1c for an example). ...
The spring dawn and dusk chorus of birds is a widespread phenomenon, yet its origin remains puzzling. We propose that a dawn and dusk chorus will inevitably arise if two criteria are met: (1) females leave their roost later in the morning and go to roost earlier in the evening than their mate, and (2) males sing more when separated from their mate. Previous studies on blue tits (Cyanistes caeruleus) support the first criterion. We here report that males sing at a higher rate whenever they are separated from their mate and that song rate increases with the duration of female absence. These findings can explain the existence of the dawn and dusk chorus in blue tits, and they can explain why the dawn chorus is more pronounced than the dusk chorus, as is typically observed. An exhaustive literature search provides support for both criteria of the ‘absent mate’ hypothesis in several passerine birds. We found no evidence contradicting the hypothesis. The new hypothesis is not inconsistent with many of the existing hypotheses about dawn singing, but may be a more general explanation for the occurrence of a dawn and dusk chorus. We describe how the ‘absent mate’ hypothesis leads to testable predictions about daily and seasonal variation in song output.
... Various studies showed that temperature is an important variable concerning metabolism in passerine birds (Dawson and Marsh 1986;Lehikoinen 1987;Cresswell 1998;Swanson Gosler 2002;Rogers and Reed 2003). In addition to temperature, the shorter photoperiod during winter season also seems to be an important factor affecting foraging because of the time available for feeding (Haftorn 1989;Steinmeyer et al. 2010;Stuber et al. 2015;Schlicht and Kempenaers 2020). However, differences in activity patterns between seasons can be the result of behavioural responses to environmental conditions to which the birds are exposed (temperature, precipitation, etc.). ...
Camera traps are increasingly used to estimate the density of animals as well as their activity patterns. As camera traps allow monitoring of animals over long periods of time without disturbance, they are especially useful to observe changes in diurnal activity patterns over time. In ornithology, camera trapping is still in its infancy. To our knowledge, no study has yet investigated the activity pattern of a songbird over the full annual cycle. We used camera traps in the Rammert, a small mountainous forest area near Rottenburg in Southwest Germany to monitor the diurnal activity pattern of forest-dwelling Eurasian blackbirds (Turdus merula). As the activity level of animals is known to be affected by day light, we used double-anchoring transformation of day times to account for the variation in sunrise and sunset across the different seasons. By generating activity models, we investigated the pattern of blackbird activity during the four seasons of the year and compared the patterns of male and female birds, respectively. A significant difference between a unimodal activity pattern in spring and a bimodal pattern for the rest of the year was found which might be related to breeding and territorial behaviour in spring. Moreover, we observed that the activity pattern of males and females overlapped greatly but still showed some variation in the number and timing of density peaks.
... To appropriately respond to weather conditions, animals have evolved a diverse array of behavioral adaptions [reviewed by 7]. In response to poor weather conditions, animals may seek shelter [8], move to lower elevations [9], alter the timing of daily activity patterns [10][11][12], change foraging strategies [13,14], delay breeding [15,16], or delay emergence from hibernation [17]. Because they spend so much of their lives in the aerosphere, flying animals such as birds are likely particularly impacted by atmospheric conditions, and weather has long been thought to alter avian behavior, including seasonal migration [18][19][20][21]. ...
Background
Weather can have both delayed and immediate impacts on animal populations, and species have evolved behavioral adaptions to respond to weather conditions. Weather has long been hypothesized to affect the timing and intensity of avian migration, and radar studies have demonstrated strong correlations between weather and broad-scale migration patterns. How weather affects individual decisions about the initiation of migratory flights, particularly at the beginning of migration, remains uncertain.
Methods
Here, we combine automated radio telemetry data from four species of songbirds collected at five breeding and wintering sites in North America with hourly weather data from a global weather model. We use these data to determine how wind profit, atmospheric pressure, precipitation, and cloud cover affect probability of departure from breeding and wintering sites.
Results
We found that the probability of departure was related to changes in atmospheric pressure, almost completely regardless of species, season, or location. Individuals were more likely to depart on nights when atmospheric pressure had been rising over the past 24 h, which is predictive of fair weather over the next several days. By contrast, wind profit, precipitation, and cloud cover were each only informative predictors of departure probability in a single species.
Conclusions
Our results suggest that individual birds actively use weather information to inform decision-making regarding the initiation of departure from the breeding and wintering grounds. We propose that birds likely choose which date to depart on migration in a hierarchical fashion with weather not influencing decision-making until after the departure window has already been narrowed down by other ultimate and proximate factors.
