Hybrid wood warblers, Dendroica striata x Dendroica castanea (Aves: Fringillidae: tribe Parulini) and the diagnostic predictability of avian hybrid phenotypes

Abstract

The plumage pattern and color and external morphology of hybrid wood warblers (Dendroica striata X Dendroica castanea) are described. This hybrid combination constitutes the only known case of hybridization between two broadly sympatric species of the genus Dendroica (Fringillidae; Tribe Parulini), that is represented by both male and female specimens in definitive alternate plumage. The plumage of the hybrids exhibited a mosaic of character states that varied in the degree of intermediacy between those of the parental species. External measurements of the hybrids fell within the cumulative ranges of characters of the postulated parental species. I hypothesize that the diagnostic predictability of hybrid phenotypes decreases as an inverse function of genetic relatedness of the hybridizing species.