Is Island Life Turning Birds into Giants? An Assessment of Foster’s Rule Across All Birds

The differences in the body sizes observed in island birds versus their closest mainland relatives have puzzled biologists for decades. First noted in other vertebrate groups by J. Foster, the general trend is usually summarized as small mainland species growing bigger on islands, while typically large mainland species are dwarfed. With many examples in both living and extinct fauna, the overall phenomenon became known as Foster’s rule (synonymous with the island rule). This study aims to examine if members of the class Aves (the group that contains all modern birds) follow the general trends of Foster’s rule and to what extent. One of the most diverse groups of vertebrates, birds are excellent colonizers of island habitats and can be found on most island systems. Using body mass, body length, and wingspan as a stand in for overall body size, data from over 9,000 extant species from around the world will be analyzed. The data will then be compiled and assessed using phylogenetic comparative techniques to account for evolutionary relationships of the main bird lineages