Does brain size matter? Linking cognitive and ecological traits to climate change vulnerability in seabirds

Abstract Understanding the mechanisms that increase a species resilience to climate change is central to predicting how they are likely to respond. One determinant of vulnerability to climate change identified in multiple taxa is the thermal range of a species' distribution. In this context, species with narrow thermal ranges are reportedly more vulnerable to climate change. One paradigm for predicting the range of environmental conditions that a species can occupy is the ‘cognitive buffer hypothesis’. The cognitive buffer hypothesis predicts that species with larger brain sizes (relative to body mass) display greater behavioural flexibility and are more able to persist and thrive within variable environmental conditions. Following the theory, we expect that species with larger relative brain sizes will occupy broader thermal ranges and be less vulnerable to climate change. In this study, we collate species‐specific information for 206 species of seabird. We then use phylogenetic generalised least squares regression and path analysis to quantify and identify linkages connecting relative brain size, thermal range, migration pattern, hand‐wing index, foraging behaviour, vulnerability to climate change and extinction risk while controlling for shared ancestry between species. We focused our study on seabirds, a highly threatened group that displays large variation in these variables. Previous work has also proposed that seabird species with a narrower thermal range across their geographic distribution are more likely to be impacted by climate change. Consistent with the cognitive buffer hypothesis, we found that seabird thermal range increases with relative brain size. We also found that having a larger relative brain size or being a long‐distance migrant may indirectly reduce extinction risk through a species' thermal range. Additionally, we found that having a higher hand‐wing index and employing generalist foraging behaviours reduces seabird vulnerability to climate change and extinction risk. Our study suggests that having a larger relative brain size, being a long‐distance migrant, employing generalist foraging behaviour and having a higher hand‐wing index can lower extinction risk. Identifying the ecological traits that promote species resilience is crucial for determining which species are most at risk of population declines to direct species conservation. Read the free Plain Language Summary for this article on the Journal blog.