Brain

Ever since Darwin, scientists have suspected that the intelligence of an animal has something to do with the size of its brain. The encephalisation theory, for example, argues that the "extra" brain tissue of a larger brain allows more neurons to be devoted to cognitive tasks. However, until now there was no scientific evidence to support this theory, partly owing to the difficulties of quantifying neuron numbers for a large number of species.

Species of birds living on islands have evolved to have larger brains than their continental relatives. Island conditions have prompted this post-colonization evolution, which enhances adaptability to environmental changes.

A large brain increases the capacity to adjust behavior to new circumstances through learning, improving resource-gathering in a changing environment. Greater understanding of this capacity can improve predictions of what species of birds and other animals will be most vulnerable to global change.