As global temperatures continue to rise, ecological and evolutionary responses in organisms are to be expected. Alongside changes in phenology and shifts in distribution, declines in body size have been suggested to represent a third universal response to climate change. Bergmann’s rule predicts that endotherms exhibit a smaller body size in warmer climates and a larger body size in colder climates. For example, up to 76% of birds have shown a trend of increasing body size with latitude. Birds serve as good indicators for environmental change. Understanding how rising temperatures affect morphology plays an important part in predicting biotic responses to global warming. Recent studies based on museum specimens suggest a consistent decline in both body size and a concurrent increase in relative wing length in bird species. Longer wings may compensate for increased flight costs associated with reduced body mass, especially in migratory birds. Wing length has also been shown to correlate positively with migratory distance. In order to investigate the correlation between climate change and morphological traits, we compare bill and wing length in museum specimens of three migratory passerine species with varying migratory strategies (Fringilla coelebs, Erithacus rubecula, Sylvia atricapilla) and one resident species (Turdus merula) from the last 100 years across natural history museums in Europe. 

This project will be conducted in collaboration with the Natural History Museum Vienna (1st Zoological Department, Ornithology).