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We provide the first comprehensive description of a bird community from a lowland rainforest site on a major island in the Solomon Islands. During two dry season visits (July 1997, June 1998) to the lower Garanga River valley on the island of Isabel, we recorded 65 resident and 6 migrant species of birds. We document relative abundances, habitat preferences, and foraging guilds for the members of the bird community. The Garanga River site sustains all but 11 of the 76 species of landbirds known from Isabel. Of those 11 species, four are small-island or beach specialists, three are montane, and four are of unknown status. Habitat heterogeneity, maintained largely by river dynamics, is a major contributor to avian diversity at the site. The avifauna is dominated by nonpasserines, especially parrots, pigeons, kingfishers, and hawks. The flightless rail Nesoclopeus woodfordi, previously regarded as rare and threatened with extinction, was common. We recorded Ixobrychus flavicollis, Falco severus, and Eudynamys scolopacea for the first time on Isabel. We also documented occurrence in the lowlands of Micropsitta finschii, Collocalia spodiopygia, Coracina caledonica, and Pachycephala pectoralis, four species previously thought to be confined to upper elevations on Isabel. The depauperate understory avifauna of the Garanga River site may be anthropogenic and could belie what otherwise seems to be an intact avifauna.

We introduce a phenotypic method to test for excess mortality in hybrids of the heterogametic sex, as expected from Haldane's rule, and apply this method to the unusually narrow hybrid zones between Hermit Warblers (Dendroica occidentalis) and Townsend's Warblers (D. townsendi) in the Pacific Northwest. Our test requires establishing comparable hybrid indices for male and female warblers. The hybrid index that we developed for females produced age-corrected distributions for phenotypically pure reference samples that closely matched those used by Rohwer and Wood (1998) for males. The similarity in these distributions enabled us to compare the relative frequency of males and females in hybrids and parentals. We detected no deficiency of hybrid females and thus no inviability in the heterogametic sex. Our failure to find evidence of the inviability component of Haldane's rule is not unexpected given the close relationship between these taxa; nonetheless, our methods should be generally useful for studies of hybrid zones.