Yellow-rumped Warbler (Setophaga coronata auduboni)

After a hard freeze overnight, these warblers were feeding in the grass. You can see ice crystals from frozen dew. This bird is a male molting into breeding plumage. The name coronata refers to the usually concealed yellow crown patch visible in this photo. This is the typical Western form S. c. auduboni formerly known as "Audubon's Warbler" showing its yellow throat. It is still treated as a separate species by IOC and HBW, but lumped with "Myrtle Warbler" by Clements and AOS based on extensive hybridization in their zone of contact in the Southern Canadian Rockies. Formerly placed in the genus Dendroica.