Shared morphological consequences of global warming in North American migratory birds

Increasing temperatures associated with climate change are predicted to cause reductions in body size, a key determinant of animal physiology and ecology. Using a four‐decade specimen series of 70 716 individuals of 52 North American migratory bird species, we demonstrate that increasing annual summer temperature over the 40‐year period predicts consistent reductions in body size across these diverse taxa. Concurrently, wing length – an index of body shape that impacts numerous aspects of avian ecology and behaviour – has consistently increased across species. Our findings suggest that warming‐induced body size reduction is a general response to climate change, and reveal a similarly consistent and unexpected shift in body shape. We hypothesise that increasing wing length represents a compensatory adaptation to maintain migration as reductions in body size have increased the metabolic cost of flight. An improved understanding of warming‐induced morphological changes is important for predicting biotic responses to global change.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153188/1/ele13434-sup-0001-Supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153188/2/ele13434.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153188/3/ele13434_am.pd

Global warming and Bergmann’s rule: do central European passerines adjust their body size to rising temperatures?

Recent climate change has caused diverse ecological responses in plants and animals. However, relatively little is known about homeothermic animals’ ability to adapt to changing temperature regimes through changes in body size, in accordance with Bergmann’s rule. We used fluctuations in mean annual temperatures in south-west Germany since 1972 in order to look for direct links between temperature and two aspects of body size: body mass and flight feather length. Data from regionally born juveniles of 12 passerine bird species were analysed. Body mass and feather length varied significantly among years in eight and nine species, respectively. Typically the inter-annual changes in morphology were complexly non-linear, as was inter-annual variation in temperature. For six (body mass) and seven species (feather length), these inter-annual fluctuations were significantly correlated with temperature fluctuations. However, negative correlations consistent with Bergmann’s rule were only found for five species, either for body mass or feather length. In several of the species for which body mass and feather length was significantly associated with temperature, morphological responses were better predicted by temperature data that were smoothed across multiple years than by the actual mean breeding season temperatures of the year of birth. This was found in five species for body mass and three species for feather length. These results suggest that changes in body size may not merely be the result of phenotypic plasticity but may hint at genetically based microevolutionary adaptations

Global temperature homogenization can obliterate temporal isolation in migratory animals with potential loss of population structure

Abstract Climate change is expected to increase the spatial autocorrelation of temperature, resulting in greater synchronization of climate variables worldwide. Possibly such ‘homogenization of the world’ leads to elevated risks of extinction and loss of biodiversity. In this study, we develop an empirical example on how increasing synchrony of global temperatures can affect population structure in migratory animals. We studied two subspecies of bar-tailed godwits Limosa lapponica breeding in tundra regions in Siberia: yamalensis in the west and taymyrensis further east and north. These subspecies share pre- and post-breeding stopover areas, thus being partially sympatric, but exhibiting temporal segregation. The latter is believed to facilitate reproductive isolation. Using satellite tracking data, we show that migration timing of both subspecies is correlated with the date of snowmelt in their respective breeding sites (later at the taymyrensis breeding range). Snow-cover satellite images demonstrate that the breeding ranges are on different climate trajectories and become more synchronized over time: between 1997 and 2020, the date of snowmelt advanced on average by 0.5 days/year in the taymyrensis breeding range, while it remained stable in the yamalensis breeding range. Previous findings showed how taymyrensis responded to earlier snowmelt by advancing arrival and clutch initiation. In the predicted absence of such advancements in yamalensis, we expect that the two populations will be synchronized by 2036–2040. Since bar-tailed godwits are social migrants, this raises the possibility of population exchange and prompts the question whether the two subspecies can maintain their geographic and morphological differences and population-specific migratory routines. The proposed scenario may apply to a wide range of (social) migrants as temporal segregation is crucial for promoting and maintaining reproductive isolation in many (partially sympatric) migratory populations. Homogenization of previously isolated populations could be an important consequence of increasing synchronized environments and hence climate change

Phenotypic signatures of urbanization are scale-dependent : a multi-trait study on a classic urban exploiter

Understanding at which spatial scales anthropogenic selection pressures operate most strongly is a prerequisite for efficient conservation and management of urban biodiversity. Heterogeneity in findings on the strength and direction of urbanization effects may result from a lack of consensus on which spatial scales are most adequate when studying biotic effects of urbanization. Therefore, here, using the house sparrow (Passer domesticus) as model, we test the hypothesis that more than one spatial scale will explain variation among phenotypic stress markers. By applying a unique hierarchical sampling design enabling us to differentiate between local and regional effects of urbanization, we here show that the strength and direction of relationships with the percentage of built-up area - a simple structural measure of urbanization - vary among phenotypic stress markers and across the spatial range over which urbanization is measured. While inverse relationships with scaled body mass and bill height of adult house sparrows (Passer domesticus) were strongest when the degree of urbanization was quantified at city-level, similar relationships with corticosterone concentrations in feathers were only detected at the scale of individual home ranges. In contrast, tarsus length, wing length, and two measures of feather development were not significantly related to urbanization at any spatial scale. As the suite of phenotypic stress markers applied in this study revealed signatures of urbanization over a broad spatial range, we conclude that measures aimed at mitigating impacts of urbanization on free-ranging populations should best be implemented at multiple spatial scales too

The end of primary moult as an indicator of global warming effects in the Red-legged Partridge Alectoris rufa, a medium sized, sedentary species

Global warming affects ecosystem services, communities and populations, influencing the physiology, behaviour or environment of living beings, and hence impacts its survival or breeding. Identifying species susceptibility to warming is relevant in assessing risks to animal populations and ecological processes. The progressive increase in ambient temperature as a result of global warming might have an effect on the timing of primary moult. This could affect a bird’s annual cycle, influencing reproductive success and population dynamics. We describe a method to examine the potential effects of global warming on the primary moult process in a sedentary population of Red-legged Partridges (Alectoris rufa). We organised the factors that might influence the timing of moult end into a network and distinguished between environmental and intrinsic factors. We sorted the factors according to their contribution to quantitative moult models and constructed a diagrammatic scheme showing their interactions and effect on the end of primary moult over the annual cycle. In Red-legged Partridges, the timing of the end of moult varies according to age-sex class. We found no timing differences by age, but found significant timing differences by adult sex. More females overlap their moult with juveniles than males because female parental effort is higher, more females incubate and brood chicks. The timing of the end of moult varies by year due to conspecific interactions that change according to influences of the weather, habitat, and social and flock conditions. Parent birds synchronize their primary moult with the chick’s growth, degree of cover and food resources. From the time of hatching to the following year, the date (day-length), social factors (conspecific interactions), and weather (resources) affect the timing of moult and the birds’ annual cycle. Global warming affects the timing of the end of moult and that of the annual cycle. If the extent of the breeding period is shortened, there could be a negative effect on population outcomes. Middle size prey species are key in trophic chains. Our results suggest that the timing of the end of moult could be used as a proxy measure of warming impacts on wildlife and ecosystems and also as a tool for the management of game birds

Eco-evolutionary consequences of dispersal syndromes during colonization in a passerine bird

In most animal species, dispersing individuals possess phenotypic attributes that mitigate the costs of colonization and/or increase settlement success in new areas (‘dispersal syndromes’). This phenotypic integration likely affects population dynamics and the direction of selection, but data are lacking for natural populations. Using an approach that combines population dynamics, quantitative genetics and phenotypic selection analyses, we reveal the existence of dispersal syndromes in a pied flycatcher (Ficedula hypoleuca) population in The Netherlands: immigrants were larger, tended to have darker plumage, bred earlier and produced larger clutches than local recruits, and some of these traits were genetically correlated. Over time, the phenotypic profile of the population gradually changed: each generation advanced arrival and breeding and exhibited longer wings as the result of direct and indirect selection on these correlated traits. Although phenotypic attributes of immigrants were favored by selection during the early phase of colonization, observed phenotypic changes were similar for immigrants and local recruits. We propose that immigrants facilitated initial population establishment but that temporal changes likely resulted from climate change-induced large scale selection. This study highlights that newly established populations are of non-random composition and that phenotypic architecture affects evolutionary population trajectories