A new hybrid warbler (Dendroica nigrescens x D-occidentalis) and diagnosisof similar D-townsendi x D-occidentalis recombinants

We use 13 color characters to describe the first known Dendroica nigrescens X D. occidentalis hybrid. Because this specimen was collected in the south eastern Cascade Mountains of Washington during the breeding season, D. town sendi, D. occidentalis, and D. nigrescens are the only plausible parents fo r a hybrid male falling within the black-throated clade of Dendroica warble rs. Multiple character states in the hybrid refute the alternative parental combinations, townsendi X occidentalis and townsendi X nigrescens. Two cha racteristics of this hybrid suggested further tests of the parentage of 38 problematic hybrids that were treated previously as townsendi X occidentali s recombinants by assumption only. These hybrids lack yellow on their breas t, the only character that refutes a nigrescens X occidentalis parentage. T he new hybrid is intermediate between nigrescens and occidentalis in the co lor of its posterior face and its anterior crown; thus, we scored these new characters in the 38 problematic hybrids. None of these 38 specimens was i ntermediate or white in either of these regions, and there was no correlati on between having tinges of white in these regions and the extent of flank streaking. These results fail to support nigrescens in the parentage of the se 38 specimens; furthermore, none of the problematic hybrids carried a nig rescens mitochondrial DNA haplotype. Thus, we conclude that all are unusual recombinants of townsendi X occidentalis hybridization, rather than nigres cens X occidentalis hybrids.