A practical guide to bird watching in Sonoma County, California

(Unless otherwise indicated, all phone numbers are in the 707 area code)


By far the most common warbler in Sonoma County from late autumn through late spring. Yellow-rumped Warblers are present year-round in the county, but their numbers increase dramatically in the winter months. The migrant population starts to arrive in mid- to late September. Numbers begin to thin again in mid-April through early May. Least common in the county in June, July, and August. According to Birds of Sonoma County, the Audubon's Warbler form (see below) greatly outnumbers the Myrtle Warbler form during migration and in winter. Usually solitary or in small groups, but, while staging to depart in the spring, may form flocks of 50 birds or more. Despite the bird's name, the yellow throat and flank patches of the Audubon's Warbler form are often much more conspicuous than the yellow rump patch. Most full adult plumages of both forms also have a yellow patch on the crown. 

Is this one species or two? Yellow-rumped Warbler was the result of the lumping of forms formerly known as "Myrtle Warbler" and "Audubon's Warbler" in 1973 (according to Kaufmann, they were lumped because the two species were known to interbreed in a zone in southwestern Alberta, Canada). Both forms have a yellow rump (although, to complicate matters, the juvenile Myrtle form lacks the yellow rump patch), but the rump is not always the most conspicuous field mark, and, in most plumages, the two forms look quite different. Nearly all guide books show the two forms of Yellow-rumped Warbler separately, and it would not be terribly surprising if they were at some point split again into distinct species. As a general rule, forms with a white throat are Myrtle Warbler (as a mnemonic, think of W for "white" being an upside-down M for "Myrtle"), while those with a yellow throat are Audubon's Warbler--but that's an oversimplification; while distinctly yellow-throated birds will always be of the Audubon's form, female Audubon's Warblers in their first fall and first spring will often have a whitish or a creamy throat. In these plumages that cause confusion because of throat color, two features are useful; Myrtle Warbler will always have a supercilium (or "eyebrow") or at least a hint of one, and the shapes of the edges of the white throat patch are different in the two forms, with Myrtle Warbler showing the white wrapping up and slightly around the back of the auricular feathers (the ear patch). In the photo above, note the supercilium and the paler throat color that turns up behind the comparatively rich, brown ear patch--both indicating Myrtle Warbler. A picture is worth many words (see below). For more, I recommend the Peterson specialty guide on warblers or The Warbler Guide.  

Note that as of July 2011, the genus Dendroica disappeared. These birds are now assigned to the genus Setophaga, but many older references will be around for a while, so expect to see this bird as Dendroica coronata, with newer sources using Setophaga coronata.

Further reading:

Bolander and Parmeter, Birds of Sonoma County California, rev. ed., 2000, p. 126

Brinkley, National Wildlife Federation Field Guide to Birds of North America, 2007, p. 384

Burridge, ed., Sonoma County Breeding Bird Atlas, 1995, p. 147

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 5th ed., 2006, p. 462

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 6th ed., 2011, p. 434

Dunn and Garrett, Warblers: Peterson Field Guides, 1st ed., 1997, pp. 267-282, pl. 12 (spanning pp. 66-67)

Ehrlich, Dobkin, and Wheye, The Birder's Handbook, paperback edition, 1988, p. 646

Fix and Bezener, Birds of Northern California, 2000, p. 314

Kaufman, Field Guide to Birds of North America, 2000, p. 308

Kaufman, Advanced Birding, 1990, pp. 229-232 (general notes on warbler ID), pp. 231, 243-245.

Kaufman, Field Guide to Advanced Birding, 2011, pp. 390-411 (general notes on warbler ID), pp. 39, 73, 106, 398-399, 402, 404-405, 411

Peterson, Birds of Eastern and Central North America, 5th ed., 2002, p. 264

Peterson, Field Guide to Birds of Western North America, 4th ed., 2010, p. 364

Peterson, Western Birds, 3rd ed., 1990,  p. 344

Peterson, Warblers, 1997, p. 267-281, pl. 12

Sibley, Field Guide to Birds of Western North America,1st ed., 2003, p. 376

Stephenson and Whittle, The Warbler Guide, 2013, 476-491

Vuilleumier, American Museum of Natural History, Birds of North America: Western Region, 2011, p. 355

Voice: Cornell Lab of Ornithology: All About Birds--Yellow-rumped Warbler



© Colin Talcroft, 2009, 2010, 2011, 2012, 2013

Unless noted, all photos by the author. If you would like to use one of my images, please ask for permission for non-commercial use with proper credit or commercial use with proper compensation.


Yellow-rumped "Myrtle" Warbler, Spring Lake, Santa Rosa, October 21, 2009

First fall female eating poison oak berries

Yellow-rumped "Audbon's" Warbler, Place-to-Play Park, Santa Rosa, February 11, 2011

Yellow-rumped "Myrtle" Warbler, Bodega Harbor, Bodega Bay, January 8, 2012

Sometimes the origin of a bird’s common name is obvious

Las Gallinas Sewer Ponds (Marin County), San Rafael, January 13, 2013

Yellow-rumped Warbler

Setophaga coronata

1990-2013 Sonoma County data. Graph provided by eBird (www.ebird.org), generated September 23, 2013

EBird reported  occurrence in Sonoma County