Shared morphological consequences of global warming in North American migratory birds

Abstract

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.

The biotic interactions hypothesis partially explains bird species turnover along a lowland Neotropical precipitation gradient

“…Neither morphological richness, dispersion nor evenness, however, were consistently higher than expected by chance. The other potential explanation is that the morphological traits we measured are not related to important niche axes for limiting resources (Ricklefs, 2012) or that the relationship between ecology and morphology is much more complex and fluid (Pigot et al, 2016;Weeks et al, 2019). It is possible that predation is stronger in wet forests, influencing community assembly (Jankowski et al, 2012;Martin, 1988b).…”

Evidence for intraspecific phenotypic variation in songbirds along elevation gradients in central Europe

“…European‐wide or even global ringing datasets have a huge potential to address questions regarding the phenotypic adaptations to different environments within the same species and their response to climate change (as there are indications for changes in morphology within recent decades; Fig. S3 and Delgado et al 2019, Weeks et al 2020). Further studies with larger biometric datasets (especially for high‐elevation populations of species) may even enable us to analyse differences in morphological variability between specialists and generalists, species of different habitat types (open grassland vs. forest) and differences in the degree of phenotypic plasticity between single species or subspecies (see Fig.…”

“…However, we also ran the same models for each individual species (without the random term) to determine the extent to which individual species associations were consistent with the overall trends. There is evidence that the biometrics of birds have changed over time in response to increasing global temperatures due to climate change (Delgado et al 2019, Weeks et al 2020). To account for possible temporal trends over our time period of 36 years, we tested the effect of year by including it as a fixed effect in the overall model and comparing Akaike information criterion (AIC) values for models with and without year.…”

“…Furthermore, studies of phenotypic variation may reveal sensitivity to environmental change. For example, recent studies have documented evidence that morphological changes in mountain birds (Delgado et al 2019) and migratory passerines (Weeks et al 2020) are correlated with climate change.…”

Peer Review #2 of "Historical museum collections and contemporary population studies implicate roads and introduced predatory bullfrogs in the decline of western pond turtles (v0.1)"

“…If museum collections are unbiased samples of species through time (a strong assumption in many cases), they can provide critical clues about population and demographic histories. For example, museum specimens have recently been utilized for multiple species as evidence of shifts in body size due to climate change (Babin-Fenske et al, 2008;Caruso et al, 2014, Weeks et al, 2019.…”