MORPHOLOGICAL DISPERSION OF THE INTRODUCED LAND-BIRDS OF SAINT-HELENA

Interspecific competition may influence the outcome of bird introducti ons on oceanic islands. Two patterns that are consistent with this hyp othesis are morphological overdispersion and priority effect. Here, we test for morphological overdispersion in the introduced passeriform b irds on the island of Saint Helena. A total of 31 passeriform species has been introduced to Saint Helena, of which five remain today. The o verwhelming majority (23) of introduced species are finches. We thus c onducted our morphological analyses on two groups; finches and all pas seriforms. The finches introduced on Saint Helena tend toward morpholo gical overdispersion; however, all passeriforms do not. We hypothesize that the pattern of overdispersion found among the finches is due to increased species richness within this group.