Predictions about the fate of species or populations under climate change scenarios typically neglect adaptive evolution and phenotypic plasticity, the two major mechanisms by which organisms can ...adapt to changing local conditions. As a consequence, we have little understanding of the scope for organisms to track changing environments by in situ adaptation. Here, we use a detailed individual-specific long-term population study of great tits (Parus major) breeding in Wytham Woods, Oxford, UK to parameterise a mechanistic model and thus directly estimate the rate of environmental change to which in situ adaptation is possible. Using the effect of changes in early spring temperature on temporal synchrony between birds and a critical food resource, we focus in particular on the contribution of phenotypic plasticity to population persistence. Despite using conservative estimates for evolutionary and reproductive potential, our results suggest little risk of population extinction under projected local temperature change; however, this conclusion relies heavily on the extent to which phenotypic plasticity tracks the changing environment. Extrapolating the model to a broad range of life histories in birds suggests that the importance of phenotypic plasticity for adjustment to projected rates of temperature change increases with slower life histories, owing to lower evolutionary potential. Understanding the determinants and constraints on phenotypic plasticity in natural populations is thus crucial for characterising the risks that rapidly changing environments pose for the persistence of such populations.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Extra-pair paternity is common among socially monogamous birds, but whether females benefit from having extra-pair copulations remains unresolved. In this study, I staged single extra-pair ...copulations in captive pairs of socially monogamous Japanese quail (
) and used extra-pair males of a different colour to identify extra-pair fertilizations. This eliminated among-female variation in extra-pair copulations as a source of variation in extra-pair fertilizations and tested whether a single extra-pair copulation would insure against infertility of the social male. Overall, the probability of extra-pair fertilization was 0.46 for the first egg that was fertilized after extra-pair copulation, but this rapidly declined over consecutive eggs in the laying sequence. However, a single extra-pair copulation was effective in ensuring fertilization of the majority of a typical clutch in the few cases where the social male was completely infertile. Hence, my results show that variation in extra-pair paternity can be independent from variation in extra-pair copulation behaviour and that a single, strategically timed, extra-pair copulation can largely insure against social male infertility. Among-female variation in extra-pair fertilizations, and their declining probability over the laying sequence, as typical for many bird species, can thus, in principle, be parsimoniously explained by a uniform female fertility insurance strategy.
The quality of the environment individuals experience during development is commonly regarded as very influential on performance in later life. However, studies that have experimentally manipulated ...the early-life environment and subsequently measured individual performance in all components of fitness over the complete life course are scarce. In this study, we incubated fertile eggs of Japanese quail (
Coturnix japonica
) at substandard and standard incubation temperature, and monitored growth, survival, and reproduction throughout the complete life course. While embryonic development was slower and hatching success tended to be lower under substandard incubation temperature, the prenatal treatment had no effect on post-hatching growth, survival to sexual maturity, or age at first reproduction. In adulthood, body mass and investment in individual egg mass peaked at middle age, irrespective of the prenatal treatment. Individual reproduction rate declined soon after its onset, and was higher in females that lived longer. Yet, reproduction, and its senescence, were independent of the prenatal treatment. Similarly, adult survival over the complete lifespan was not affected. Hence, we did not find evidence for effects on performance beyond the developmental period that was manipulated. Our results suggest that effects of unfavorable developmental conditions on individual performance later in life could be negligible in some circumstances.
Understanding the evolution of migration requires knowledge of the patterns, sources, and consequences of variation in migratory behaviour, a need exacerbated by the fact that many migratory species ...show rapid population declines and require knowledge-based conservation measures. We therefore need detailed knowledge on the spatial and temporal distribution of individuals across their annual cycle, and quantify how the spatial and temporal components of migratory behaviour vary within and among individuals.
We tracked 138 migratory journeys undertaken by 64 adult common terns (Sterna hirundo) from a breeding colony in northwest Germany to identify the annual spatiotemporal distribution of these birds and to evaluate the individual repeatability of eleven traits describing their migratory behaviour.
Birds left the breeding colony early September, then moved south along the East Atlantic Flyway. Wintering areas were reached mid-September and located at the west and south coasts of West Africa as well as the coasts of Namibia and South Africa. Birds left their wintering areas late March and reached the breeding colony mid-April. The timing, total duration and total distance of migration, as well as the location of individual wintering areas, were moderately to highly repeatable within individuals (repeatability indexes: 0.36-0.75, 0.65-0.66, 0.93-0.94, and 0.98-1.00, respectively), and repeatability estimates were not strongly affected by population-level inter-annual variation in migratory behaviour.
We found large between-individual variation in common tern annual spatiotemporal distribution and strong individual repeatability of several aspects of their migratory behaviour.
While life‐history theory predicts a tradeoff between reproduction and survival, positive covariance, indicative of heterogeneity in individual quality, is often reported among individuals from ...natural populations. We review longitudinal studies of wild bird populations that test the relationship between annual reproductive success and lifespan and find the majority to report a positive correlation, while none reports a negative correlation. Heterogeneity in individual quality in resource acquisition, masking resource‐based tradeoffs, therefore appears to be common in birds. Considering that there is little evidence for heritable variation in fitness, heterogeneity in individual quality among adults may be due to life‐long effects of developmental conditions. In a 20‐year case study on common terns Sterna hirundo, we test for life‐long effects of cohort quality and within‐cohort nest quality, but find no significant effects on long‐term proxies of quality. Since other studies do find strong life‐long effects of developmental conditions, we suggest that the brood reduction strategy adopted by common terns, causing the majority of offspring to die rapidly after hatching, efficiently reduces variation in offspring quality at independence. As such, a brood reduction strategy may contribute to reduced heterogeneity in adult survival in stochastic environments, both suggested to be more common and adaptive in long‐lived species. Further study is required to assess heterogeneity in individual reproduction, especially in relation to environmental stochasticity and species’ life‐history strategies, in order to assess whether the relative strength of selection in early and late life may indeed affect the magnitude of heterogeneity in individual quality over life, and how this is mediated by parent–offspring conflict.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Most birds have specific habitat requirements for breeding. The vegetation structure surrounding nest-sites is an important component of habitat quality, and can have large effects on avian breeding ...performance. We studied 13 years of Blue Tit Cyanistes caeruleus population data to determine whether characteristics of vegetation structure predict site occupancy, laying date and number of eggs laid. Measurements of vegetation structure included the density of English Oak Quercus robur, European Beech Fagus sylvatica, and other deciduous, coniferous and non-coniferous evergreen trees, within a 20-m radius of nest-boxes used for breeding. Trees were further sub-divided into specific classes of trunk circumferences to determine the densities for different maturity levels. Based on Principal Component Analysis (PCA), we reduced the total number of 17 measured vegetation variables to 7 main categories, which we used for further analyses. We found that the occupancy rate of sites and the number of eggs laid correlated positively with the proportion of deciduous trees and negatively with the density of coniferous trees. Laying of the first egg was advanced with a greater proportion of deciduous trees. Among deciduous trees, the English Oak appeared to be most important, as a higher density of more mature English Oak trees was associated with more frequent nest-box occupancy, a larger number of eggs laid, and an earlier laying start. Furthermore, laying started earlier and more eggs were laid in nest-boxes with higher occupancy rates. Together, these findings highlight the role of deciduous trees, particularly more mature English Oak, as important predictors of high-quality preferred habitat. These results aid in defining habitat quality and will facilitate future studies on the importance of environmental quality for breeding performance.
•We examined habitat-related occupancy, lay date and clutch size in Blue Tits.•In deciduous habitat with mature English Oaks breeding sites were more often occupied.•Birds also laid earlier, and clutches were larger, in this habitat type.•Hence, occupancy rate is a reliable indicator of the quality of breeding sites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In seasonally reproducing organisms, timing reproduction to match food availability is key to individual fitness. Ambient temperature functions as an important cue for the timing of the food peak in ...temperate-zone birds. After laying start, individual birds may still improve synchrony between offspring hatching and food availability by adjusting the onset of incubation to most up-to-date cues about the development of the food source. However, it is unknown whether individuals respond to changes in temperature after the onset of laying, and whether individuals adjust incubation onset independent of clutch size. Here, I show in free-living blue tits (Cyanistes caeruleus) that experimental heating of nestboxes in the laying phase resulted in increased duration of nocturnal incubation bouts prior to clutch completion, leading to earlier hatching of eggs and increased hatching asynchrony. Experimental heating did not affect the number of laying gaps, egg volume and clutch size, nor were any carry-over effects on offspring detected. These results are best explained as a response to increased temperature acting as a cue for an advanced food-peak, rather than a relief of energetic constraints, because improved energetic conditions would not favour more hatching asynchrony. Other benefits cannot be excluded, since increased laying-phase incubation under warmer conditions may also help maintain egg viability. This study is the first to show that temperature has a causal effect on the time between clutch completion and hatching of the first offspring, indicating that behavioural adjustment to climate change can continue after laying start.
Evolutionary theory suggests that individuals can benefit from deferring the fitness cost of developing under poor conditions to later in life. Although empirical evidence for delayed fitness costs ...of poor developmental conditions is abundant, individuals that die prematurely have not often been incorporated when estimating fitness, such that age‐specific fitness costs, and therefore the relative importance of delayed fitness costs are actually unknown.
We developed a Bayesian statistical framework to estimate age‐specific reproductive values in relation to developmental conditions. We applied it to data obtained from a long‐term longitudinal study of common terns Sterna hirundo, using sibling rank to describe variation in developmental conditions. Common terns have a maximum of three chicks, and later hatching chicks acquire less food, grow more slowly and have a lower fledging probability than their earlier hatched siblings.
We estimated fitness costs in adulthood to constitute c. 45% and 70% of the total fitness costs of hatching third and second, respectively, compared to hatching first. This was due to third‐ranked hatchlings experiencing especially high pre‐fledging mortality, while second‐ranked hatchlings had lower reproductive success in adulthood. Both groups had slightly lower adult survival. There was, however, no evidence for sibling rank‐specific rates of senescence.
We additionally found years with low fledgling production to be associated with particularly strong pre‐fledging selection on sibling rank, and with increased adult survival to the next breeding season. This suggests that adults reduce parental allocation to reproduction in poor years, which disproportionately impacts low‐ranked offspring.
Interpreting these results, we suggest that selection at the level of the individual offspring for delaying fitness costs is counteracted by selection for parental reduction in brood size when resources are limiting.
The authors partition the lifetime fitness consequences of poor early‐life conditions over age in a long‐lived seabird. Their results suggest that selection on parents may favour earlier expression of negative fitness consequences than selection on the offspring.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Female birds can influence offspring fitness by varying the relative quantities of egg components they deposit within and between clutches. Antimicrobial proteins (lysozyme, ovotransferrin, and ...avidin) are significant components of the avian albumen and likely aid in defense of embryos from microbial infection. Within clutches, females may enhance antimicrobial defense of early-laid eggs to protect them from the high risk of infection incurred before the onset of incubation. Among entire clutches, females may invest more resources in young sired by more attractive males because they have higher reproductive value. We tested these hypotheses by quantifying antimicrobial protein distribution within and among clutches in blue tit eggs. Contrary to our hypothesis, clutches showed no differential deposition of lysozyme or avidin within clutches, but eggs laid in the middle of the sequence had higher concentrations of ovotransferrin than eggs in the beginning and end. Consistent with our second hypothesis, we found that females produced eggs with higher concentrations of lysozyme (although not ovotransferrin or avidin) when mated to more attractive (more UV-reflective) males. Furthermore, females mated to polygynous males deposited less lysozyme than those mated to monogamous males. These data suggest that allocation of lysozyme at the clutch level may be a maternal effect mediated by male qualities.
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