Food specialization and radiation of Hawaiian honeycreepers

Abstract

Hawaiian honeycreepers are renowned for adaptive radiation and diet specialization. Specialization arose from competition for the relatively few resources available in this remote archipelago and because arthropod prey sufficient to satisfy nestling protein requirements could only be captured by highly modified bills. Historically, most species fed their nestlings with larvae of the widespread geometrid moth genus, Scotorythra ; but other invertebrates were important also. Thus the palila, Loxioides bailleui , a specialist on potentially toxic Sophora chrysophylla seeds, feeds its nestlings on Cydia moth larvae found inside Sophora seeds. Sophora seeds are also fed to the nestlings, and seed availability largely determines the timing and extent of breeding. By this and other means, food specialization contributed to reproductive isolation in Loxioides and possibly other honeycreepers. Alien threats to insect prey affect Loxioides populations and have hastened the extinction or decline of other specialized Hawaiian birds