Phenotypic responses to climate change are significantly dampened in big‐brained birds

Anthropogenic climate change is rapidly altering local environments and threatening biodiversity throughout the world. Although many wildlife responses to this phenomenon appear largely idiosyncratic, a wealth of basic research on this topic is enabling the identification of general patterns across taxa. Here, we expand those efforts by investigating how avian responses to climate change are affected by the ability to cope with ecological variation through behavioural flexibility (as measured by relative brain size). After accounting for the effects of phylogenetic uncertainty and interspecific variation in adaptive potential, we confirm that although climate warming is generally correlated with major body size reductions in North American migrants, these responses are significantly weaker in species with larger relative brain sizes. Our findings suggest that cognition can play an important role in organismal responses to global change by actively buffering individuals from the environmental effects of warming temperatures. Anthropogenic climate change is rapidly altering local environments and wildlife responses appear largely idiosyncratic. We investigated how avian phenotypic responses to climate change are affected by the ability to cope with ecological variation through behavioral flexibility (as measured by relative brain size). After accounting for the effects of phylogenetic uncertainty and across‐species variation in adaptive potential, we confirm that although warming temperatures drive major body size reductions in North American migrants, these reductions are significantly weaker in species with larger relative brain sizes.