Ecomorphological pattern in Bermuda birds: The influence of competition and implications for nature preserves

Abstract

Previous ecomorphological studies of introduced land birds on oceanic islands have revealed several patterns consistent with the hypothesis that interspecific competition influenced the assembly process of that community. We extend one of these analyses to Bermuda, which differs from the previous islands in its size, latitude and isolation from the mainland. We tested for the presence of morphological overdispersion in surviving introduced passeriforms. Despite a possible predominance of random events in the assembly process due to Bermuda's small size and the presence of migrant species, the surviving passeriforms were morphologically overdispersed. The presence of this pattern supports the hypothesis that the assembly of the Bermuda passeriform community has been influenced by interspecific competition. This marks the third distinct community of island land birds in which this competitive pattern has been identified. This is particularly interesting because certain attributes of Bermuda and its avifauna make it more equivalent to communities in mainland refuges than avian assemblages on islands studied previously. This suggests that interspecific competition may have important effects on the structure of refuge communities.