Patterns of Extinction in the Introduced Hawaiian Avifauna: A Reexamination of the Role of Competition

Abstract

Among introduced passeriform and columbiform birds of the six major Hawaiian islands, some species (including most of those introduced early) may have an intrinsically high probability of successful invasion, whereas others (including many of those introduced from 1900 through 1936) may be intrinsically less likely to succeed. This hypothesis accords well with the observation that, of the 41 species introduced on more than one of the Hawaiian islands, all but four either succeeded everywhere they were introduced or failed everywhere they were introduced, no matter what other species or how many other species were present. Other hypotheses, including competitive ones, are possible. However, most other patterns that have been claimed to support the hypothesis that competitive interactions have been key to which species survived are ambiguous. We propose that the following patterns are true: (1) Extinction rate as a function of number of species present (S) is not better fit by addition of an S2 term. (2) Bi...