Palm Warbler

A very unusual fall migrant in Sonoma County, Palm Warbler may also turn up from time to time in the winter months or in the spring. There are at least two distinct Palm Warbler populations. One (Setophaga palmarum hypochrysea or "Yellow Palm Warbler") nests from Quebec and eastward, the western population (Setophaga palmarum palmarum or "Western Palm Warbler") nests west of Quebec. It's birds from the latter group we usually see in Sonoma County, although there are a few West Coast records of birds from the eastern population as well. The bird pictured above is typical of the western race (details below). Older sources will list this species as Dendroica palmarum. Although Palm Warbler is not common here, Lukas notes that it’s the most common vagrant warbler in the Bay Area.

Western Palm Warbler in the plumage we usually see is pale brown above with a pale, finely streaked breast that shades from a light, nearly-white, butter yellow above to a darker butter yellow at the lower belly and under the tail. The yellow is quite variable, but the undertail coverts are always yellow. The cap is dark with a hint of rufous. That and a dark eyeline create a strong white eyebrow. Look for a faint brown auricular patch (brownish cheek) and hints of yellow at the base of the throat and at the lores as well. There is often a suggestion of a fine white half eye-ring below the eye. The chin and extreme upper breast may be whiter than the surrounding areas. In breeding plumage, the cap becomes rufous and the head acquires more yellow, with rufous streaking. The Yellow Palm Warbler is considerably more yellow in nearly all plumages than the Western race. It’s useful to remember, however, that the Western Palm Warbler is yellow under the tail in all plumages, as noted above. The pattern of white on the underside of the tail (photo below) is distinctive as well. This warbler tends to stay low to the ground or on the ground, foraging for food. Often bobs its tail like a wagtail.

Selected county sightings: Eastshore Rd., Bodega Bay (November 18, 2012, Lisa Hug); Bay Flat Rd. (October 13, 2012, Colin Talcroft); Diekmann’s Bay Store (October 12, 2012, Dea Fried); Hole in the Head (October 1, 2012, Colin Talcroft); Reclamation Rd. (February 18, 2012, Peter Colasanti); Cypress Hill Memorial Park, Petaluma (February 5-12, 2012, Dan Nelson); Ordinance Rd. (March 3, 2011)