Relationships between winter temperature and breeding bird abundance on community level: importance of interspecific differences in diet

Winter weather limits populations of resident bird species. Although many small-scale or species-specific studies illustrated this fact, our knowledge of interspecific differences in population responses to winter temperatures is incomplete due to lack of community-level studies. For this purpose, we have used long-term monitoring data on breeding bird populations of 37 common bird species wintering in the Czech Republic. We predicted that species will differ in their relationship between winter temperature and abundance with respect to their body mass and dietary niche. Smaller species having relatively higher energy expenditure should show closer relationship between breeding abundance and winter temperature than larger species. Concerning dietary niche, abundance of species feeding on animals should be more affected by temperature than abundance of species feeding on plants or omnivorous species. Our results confirmed the second prediction: populations of species preying on animals followed winter temperatures more closely than populations of species feeding on both animals and plants. Food-mediated mortality is probably more important than direct effects of low temperatures. In general, relationships between abundance and temperature were relatively weak in most species and we suggest that possible changes in winter temperatures may not seriously affect populations of common breeding birds in the Czech Republic.