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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 (Dendroica coronata).

Classification

Since 1973, the American Ornithologists' Union has elected to merge these passerine birds as one species. The Myrtle form was apparently separated from the others by glaciation during the Pleistocene, and the Audubon's form may have originated more recently through hybridization between the Myrtle Warbler and the Mexican nigrifrons form. [1]

Distribution

The Yellow-rumped Warbler breeds from eastern North America west to the Pacific, and southward from there into Western Mexico. "Goldman's" Yellow-rumped Warbler is endemic to the highlands of Guatemala. The Myrtle and Audubon's forms are migratory, traveling to the southern U.S., Mexico, Central America, and the Caribbean for winters. Among warblers it is one of the last to leave North America in the fall, and among the first to return. It is an occasional vagrant to the British Isles and Iceland.

Description

In summers, males of both forms have streaked backs of black on slate blue, white wing patches, a streaked breast, and conspicuous yellow patches on the crown, flank, and rump. Audubon's Warbler also sports a yellow throat patch, while the Myrtle Warbler has a white throat and eye stripe, and a contrasting black cheek patch. Females of both forms are more dull, with brown streaking front and back, but still have noticeable yellow rumps. Goldman's Warbler, of Guatemala, resembles Audubon's but has a white lower border to the yellow throat and otherwise darker plumage; males replace the slate blue of Audubon's with black.

These birds are primarily insectivorous, although when bugs are scarce, the Myrtle Warbler also enjoys eating the wax-myrtle berries which gave it its name. They often flit, flycatcher-like, out from their perches in short loops, in search of insects.

They nest in coniferous and mixed woodlands, and lay 4–5 eggs in a cup-shaped nest.

The Yellow-rumped has a trill-like song of 4–7 syllables (tyew-tyew-tyew-tyew,tew-tew-tew) and an occasional check or chip call note.

References

BirdLife International (2004). Dendroica coronata. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 10 May 2006. Database entry includes justification for why this species is of least concern
Howell, Steve N. G., and Sophie Webb (1994). A Guide to the Birds of Mexico and Northern Central America. Oxford University Press. ISBN 0-19-854012-4.

^ Brelsford, Alan; Milá, Borja; Irwin, Darren E.. "Hybrid origin of Audubon's warbler". Molecular Ecology in press. doi:10.1111/j.1365-294X.2011.05055.x.

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