Morphological dispersion of the introduced land-birds of saint helena

Lockwood, J.L., Moulton, M.P. … Brooke, R.K. 1996. Morphological dispersion of the introduced land-birds of Saint Helena. Ostrich 67: 111–117. Interspecific competition may influence the outcome of bird introductions on oceanic islands. Two patterns that are consistent with this hypothesis are morphological overdispersion and priority effect. Here, we test for morphological overdispersion in the introduced passeriform birds on the island of Saint Helena. A total of 31 passeriform species has been introduced to Saint Helena, of which five remain today. The overwhelming majority (23) of introduced species are finches. We thus conducted our morphological analyses on two groups; finches and all passeriforms. The finches introduced on Saint Helena tend toward morphological 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.