Yellow-rumped Warbler (Setophaga coronata auduboni)
Best viewed large.
Found this guy at Belmont Pond, Kelowna, BC.
Also known as Audubon's Warbler and 'butter butts'.
Four closely related North American bird forms—the eastern myrtle warbler (ssp coronata), its western counterpart, Audubon's warbler (ssp group auduboni), the northwest Mexican black-fronted warbler (ssp nigrifrons), and the Guatemalan Goldman's warbler (ssp goldmani)—are periodically lumped as the yellow-rumped warbler (Setophaga coronata)
This guy is Audubon's warbler (Setophaga auduboni or Setophaga coronata auduboni).
The New World warblers or wood-warblers are a group of small, often colorful, passerine birds which make up the family Parulidae and are restricted to the New World. They are not closely related to Old World warblers or to Australian warblers. Most are arboreal, but some, like the ovenbird and the two waterthrushes, are primarily terrestrial. Most members of this family are insectivores.
It is likely that this group originated in northern Central America, where the greatest number of species and diversity between them is found. From there they spread north during the interglacial periods, mainly as migrants, returning to the ancestral region in winter.