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60 results for “timing of breeding”
Autumn departure from breeding site (date and time) in Gambel's white crowned sparrows near Toolik Field Station, Alaska, summers 2014-2016
This data set contains information about an automated radio-telemetry study conducted near Toolik Field Station examining the date that adult male and female Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelli) depart the breeding site relative to the timing of breeding and sunrise/ sunset. It was funded, in part, through ARC 0909133 (to John Wingfield) and ARC 1147289 (to Marilyn Ramenofsky). It is associated with publication: https://doi.org/10.1007/s10336-020-01754-z.
Relative breeding timing and reproductive success of a resident montane bird species
<p>The phenological match-mismatch hypothesis predicts that animals that better synchronize critical life history events with the peak availability of their primary food source should have higher fitness. If phenological match-mismatch determines breeding success, most individuals in a population may be expected to breed simultaneously within a given year because selection has favored mechanisms that allow for the tracking of optimal food abundance. Therefore, individuals that breed too early or too late relative to the bulk of the population ("peak" of breeding) should experience decreased fitness. Using 11 years of data, we investigated the effect of relative breeding timing on breeding success in resident mountain chickadees (Poecile gambeli) across two elevations in the Sierra Nevada mountains, USA. Chickadees that bred during the peak of nesting did not have the highest breeding success; instead, birds that bred earliest performed best at high elevation, while at low elevation early and peak nests performed similarly. Breeding success decreased linearly with relative timing at both high and low elevations, and the relationship between breeding success and timing differed among years. Our results suggest that phenological match-mismatch may not be the main driver of within-year variation in breeding success in animals residing in montane environments.</p>
No relationship between chronotype and timing of breeding when variation in daily activity patterns across the breeding season is taken into account
<p>There is increasing evidence that individuals are consistent in the timing of their daily activities, and that individual variation in temporal behaviour is related to the timing of reproduction. However, it remains unclear whether observed patterns relate to the timing of the onset of activity or whether an early onset of activity extends the time that is available for foraging. This may then again facilitate reproduction. Furthermore, the timing of activity onset and offset may vary across the breeding season, which may complicate studying the above mentioned relationships. Here, we examined in a wild population of great tits (Parus major) whether an early clutch initiation date may be related to an early onset of activity and/or to longer active daylengths. We also investigated how these parameters are affected by the date of measurement. In order to test these hypotheses we measured emergence and entry time from/into the nest box as proxies for activity onset and offset in females during the egg laying phase. We then determined active daylength. Both emergence time and active daylength were related to clutch initiation date. However, a more detailed analysis showed that the timing of activities with respect to sunrise and sunset varied throughout the breeding season both within and among individuals. The observed positive relationships are hence potentially statistical artifacts. After methodologically correcting for this date effect, by using data from the pre-egg laying phase, where all individuals were measured on the same days, neither of the relationships remained significant. Taking methodological pitfalls and temporal variation into account may hence be crucial for understanding the significance of chronotypes.</p>
Fig. 1 in Pantala flavescens successfully breeding for the second time in Malta (Maltese Archipelago) (Odonata: Libellulidae)
Fig. 1 – The four reservoirs where male Pantala flavescens were seen holding territory and from where the exuviae were collected.
Data for: Similar environmental cues guide timing of breeding and seasonal shifts in songbird social structure
<p>Seasonally breeding animals often exhibit different social structures during non-breeding and breeding periods that coincide with seasonal environmental variation. Therefore, ongoing climate change may play an important role in determining the future structure of animal societies, especially if climate determines when seasonal shifts in social structure occur. However, we know little about the environmental cues that determine the timing of seasonal shifts in social structure, a lack of knowledge that contrasts with our well-defined knowledge of the environmental cues that trigger a shift to breeding physiology in seasonally breeding species. Here we tested whether the environmental cues that drive seasonal shifts in social structure are similar to those that determine timing of breeding in the red-backed fairywren (<em>Malurus melanocephalus</em>), an Australian songbird. Social network analyses revealed that social groups, which are highly territorial during the breeding season, interact in social "communities" on larger ranges during the non-breeding season. Interactions among non-breeding groups were related to rainfall, with more rainfall leading to reductions in home range size and fewer interactions among non-breeding social groups. Similarly, onset of breeding was also determined by rainfall during the non-breeding season, with greater rainfall leading to earlier breeding. These findings reveal that for some species, the cues that determine the timing of shifts in social structure across seasonal boundaries can be similar to those that determine timing of breeding. This study increases our understanding of how social structure and the selection pressures that result from different social structures might respond to changing climates.</p>
Timing of migration and African non-breeding grounds of geolocator-tracked Pied Flycatchers: A multi-population assessment
<p>We provide raw geolocator data from eight pied flycatchers tracked by light geolocators from breeding sites in the Czech Republic.</p> <p>Geolocator model GDL2.0 with 7 mm light stalk, producer Swiss Ornithological Institute. A script for R with calibration method for the equinox period is provided.</p>
Data from: Time series of bird abundances, land cover and temperature from standardized breeding bird monitoring schemes (line transects and point count routes) from Norway, Sweden and Finland, for 1975-2016
<p><span>These data on bird species abundance and environmental variables were used in testing and comparing two different species distribution model validation methods that are applied to models which are used to predict the effects of climate change on species' distributions. The aim of the study was to investigate whether different validation methods give different results of the model's predictive performance and to demonstrate that validation methods based on measuring and validating a "static" pattern in distribution can assess model performance over-optimistically compared to methods based on measuring and validating a "change" in the distribution, which can assess the predictive performance more critically. </span></p>
Breeding season forest fragment size does not create negative carry-over for adult Wood Thrushes on fall migration timing or apparent annual survival
<p>Although carry-over effects related to wintering habitat quality are known to influence population dynamics of migratory songbirds, the presence of breeding season carry-over is under-studied in full annual cycle models. To test whether forest fragment size on the breeding grounds can impose negative carry-over effects on a migratory songbird, we fitted adult Wood Thrushes with one-year coded radio-tags in forest fragments ranging from 11–499 ha in southwestern Ontario during the 2016–2019 breeding seasons and utilized automated telemetry via the Motus Wildlife Tracking System to record fall migration timing and returns the following spring (apparent annual survival). To examine short-term effects of fragment size on breeding females, during the 2018 and 2019 breeding seasons, we collected blood samples during incubation to measure corticosterone levels and tracked complete reproductive success and nest timing. We found that Wood Thrushes breeding in small forest fragments were not subject to strong negative effects on body condition (mass, corticosterone), reproductive success, or timing of the last nest of the season. Next, we found that the onset of fall migration departure was not delayed for birds nesting in small fragments and that apparent annual survival was not linked to breeding fragment size. This suggests that habitat differences linked to fragment size were not strong enough to trigger the kinds of negative carry-over effects (delayed migration, lower reproductive success) that have been documented in other species as a result of poor wintering ground habitat quality. The strength of breeding fragment size-induced seasonal carry-over remains a critical gap in full annual cycle models for other declining migratory songbirds. Our findings suggest that while the importance of preserving large forested areas is often prioritized in conservation projects, small forest fragments can also have high conservation value.</p>
No relationship between chronotype and timing of breeding when variation in daily activity patterns across the breeding season is taken into account
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Relative breeding timing and reproductive success of a resident montane bird species
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Data from: Time series of bird abundances, land cover and temperature from standardized breeding bird monitoring schemes (line transects and point count routes) from Norway, Sweden and Finland, for 1975-2016
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Data from: Dissecting factors behind temporal trends in the timing of breeding in two songbird species – evolutionary change or phenotypic plasticity?
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Breeding season forest fragment size does not create negative carry-over for adult Wood Thrushes on fall migration timing or apparent annual survival
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Population density and timing of breeding mediate effects of early life conditions on recruitment
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Multidimensional plasticity of phenology: Assessing the effects of population density on plastic responses of breeding time to temperature
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Data from: Shifts in timing and duration of breeding for 73 boreal bird species over four decades
<p>Breeding timed to match optimal resource abundance is vital for the successful reproduction of species, and breeding is therefore sensitive to environmental cues. As the timing of breeding shifts with a changing climate, this may not only affect the onset of breeding, but also its termination, and thus the length of the breeding period. We use an extensive dataset of over 820K nesting records of 73 bird species across the boreal region in Finland to probe for changes in the beginning, end, and duration of the breeding period over four decades (1975-2017). We uncover a general advance of breeding with a strong phylogenetic signal, but no systematic variation over space. Additionally, 31% of species contracted their breeding period in at least one bioclimatic zone, as the end of the breeding period advanced more than the beginning. We did not detect a statistical difference in phenological responses of species with combinations of different migratory strategy or number of broods. Nonetheless, we find systematic differences in species responses, as the contraction in the breeding period was found almost exclusively in resident and short-distance migrating species, which generally breed early in the season. Overall, changes in the timing and duration of reproduction may potentially lead to more broods co-occurring in the early breeding season – a critical time for species' reproductive success. Our findings highlight the importance of quantifying phenological change across species and over the entire season, to reveal shifts in the community-level distribution of bird reproduction.</p>
Data from: The effects of food supply on reproductive hormones and timing of reproduction in an income-breeding seabird
<p class="CxSpFirst">Current food supply is a major driver of timing of breeding in income-breeding animals, likely because increased net energy balance directly increases reproductive hormones and advances breeding. In capital breeders, increased net energy balance increases energy reserves, which eventually leads to improved reproductive readiness and earlier breeding. To test the hypothesis that phenology of income-breeding birds is independent of energy reserves, we conducted an experiment on food-supplemented ("fed") and control female black-legged kittiwakes (<em>Rissa tridactyla</em>). We temporarily increased energy costs (via weight handicap) in a 2 × 2 design (fed/unfed; handicapped/unhandicapped) during the pre-laying period and observed movement via GPS-accelerometry. We measured body mass, baseline hormones (corticosterone; luteinising hormone) before and after handicap manipulation, and conducted a gonadotropin-releasing hormone challenge. Females from all treatment groups foraged in similar areas, implying that individuals could adjust time spent foraging, but had low flexibility to adjust foraging distance. Consistent with the idea that income breeders do not accumulate reserves in response to increased food supply, fed birds remained within an energy ceiling by reducing time foraging instead of increasing energy reserves. Moreover, body mass remained constant until the onset of follicle development 20 days prior to laying regardless of feeding or handicap, implying that females were using a 'lean and fit' approach to body mass rather than accumulating lipid reserves for breeding. Increased food supply advanced endocrine and laying phenology and altered interactions between the hypothalamic-pituitary-adrenal axis and the hypothalamic-pituitary-gonadal axis, but higher energy costs (handicap) had little effect. Consistent with our hypothesis, increased food supply (but not net energy balance) advanced endocrine and laying phenology in income-breeding birds without any impact on energy reserves.</p>
Plasticity in female timing may explain earlier breeding in a North American songbird
<p>Many species have shifted their breeding phenology in response to climate change. Identifying the magnitude of phenological shifts and whether climate-mediated selection drives these shifts is key for determining species' resilience to climate change. Birds are a strong model for studying phenological shifts due to numerous long-term research studies; however, generalities pertaining to drivers of phenological shifts will emerge only as we add study species that differ in life history and geography. We investigated 32 years of reproductive timing in a non-migratory population of dark-eyed juncos (Junco hyemalis). We predicted that plasticity in reproductive timing would allow females to breed earlier in warmer springs. We also predicted that selection would favour earlier breeding, and we asked whether temperatures throughout the breeding season would predict the strength of selection. To test these predictions, we examined temporal changes in the annual median date for reproductive onset (i.e., first egg date), and we used a sliding window analysis to identify monthly spring temperatures driving these patterns. Next, we explored plasticity in reproductive timing and asked whether selection favoured earlier breeding. Lastly, we used a sliding window analysis to identify the time during the breeding season that temperature was most associated with selection favouring earlier breeding. First egg dates occurred earlier over time and strongly covaried with April temperatures. Further, for individual females that bred in more than one year, they typically bred earlier in warmer Aprils, exhibiting plastic responses to April temperature. We also found significant overall selection favouring earlier breeding (i.e., higher relative fitness with earlier first egg dates) and variation in selection for earlier breeding over time. However, temperature across diverse climatic windows did not predict the strength of selection. Our findings provide further evidence for the role of phenotypic plasticity in shifting phenology in response to earlier springs. We provide evidence for the role of selection favouring earlier breeding, regardless of temperature, thus setting the stage for adaptive changes in female breeding phenology. We suggest for multi-brooded birds that advancing first egg dates likely increases the length of the breeding season, and therefore, reproductive success.</p>
Fig. 3 in Pantala flavescens successfully breeding for the second time in Malta (Maltese Archipelago) (Odonata: Libellulidae)
Fig. 3 – Two teneral specimens of Pantala flavescens.
Local timing of rainfall predicts the timing of moult within a single locality and the progress of moult among localities that vary in the onset of the wet season in a year-round breeding tropical songbird
<p>Rainfall seasonality is likely an important cue for timing key annual cycle events like moult in birds living in seasonally arid environments, but its precise effect is difficult to establish because seasonal rainfall may affect other covarying annual events such as breeding in the same way. In central Nigeria, however, Common Bulbuls <em>Pycnonotus barbatus</em> moult in the wet season but only show weak breeding seasonality. This suggests that moult is more sensitive to rainfall than breeding, but a similar outcome is possible if moult is simply periodic. We tested the relationship between rainfall and moult in Common Bulbuls at a single location over 18 years: on average moult started 5th May (± 41 days: 25th March–15th June), being on average later than the onset of the rains which is usually mid-April. The likelihood of finding a moulting Common bulbul was best predicted by rainfall 9–15 weeks before moult was scored. We then tested the generality of this across populations: the progress of moult should, therefore, correlate with the average timing of the wet season along a spatial environmental gradient where the rains start at different times each year south-to-north of Nigeria. To test this, we modelled moult progress just before the rains across 15 localities 6°–13° N as a function of the onset of the wet season among localities. As predicted, moult progressed further in localities with earlier wet seasons, confirming that the onset of moult is timed to the onset of the wet season in each locality despite weak breeding seasonality in the Common Bulbul. This strategy may evolve to maintain optimal annual cycle routine in seasonal environments where breeding is prone to unpredictable local perturbations like nest predation. It may, however, be less obvious in temperate systems where all annual cycle stages are seasonally constrained, but it may help with explaining the high frequency of breeding–moult overlaps in tropical birds.</p>
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