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

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 expected 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
(PGLS) 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 wider 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 and directing species conservation.