Big brains, enhanced cognition, and response of birds to novel environments

Abstract

The widely held hypothesis that enlarged brains have evolved as an adaptation to cope with novel or altered environmental conditions lacks firm empirical support. Here, we test this hypothesis for a major animal group (birds) by examining whether large-brained species show higher survival than small-brained species when introduced to nonnative locations. Using a global database documenting the outcome of >600 introduction events, we confirm that avian species with larger brains, relative to their body mass, tend to be more successful at establishing themselves in novel environments. Moreover, we provide evidence that larger brains help birds respond to novel conditions by enhancing their innovation propensity rather than indirectly through noncognitive mechanisms. These findings provide strong evidence for the hypothesis that enlarged brains function, and hence may have evolved, to deal with changes in the environment.

Fig. 1

Relationship between mean relative brain size and invasion potential for worldwide avian families. The relationship is shown without (A) and with (B) control for phylogenetic effects by using independent contrast analysis.

Fig. 2

Relationship between mean feeding innovation propensity and invasion potential for Palearctic avian families. The relationship is shown without (A) and with (B) control for phylogenetic effects by using independent contrast analysis..

Fig. 3

Path diagram depicting two causal models for the relationship between relative brain size, residual innovation propensity (i.e., corrected for research effort), and invasion potential for Palearctic avian families.