Editor's Note: Phylogenetic analyses of sequences of mitochondrial and nuclear DNA indicate that all species formerly placed in Dendroica, one species formerly placed in Wilsonia (citrina), and two species formerly placed in Parula (americana and pitiayumi) form a clade with the single species traditionally placed in Setophaga (ruticilla). The generic name Setophaga has priority for this clade. See the 52nd Supplement to the AOU Checklist of North American Birds for details. Future revisions of this account will reflect these changes.
A colorful, distinctive wood-warbler that breeds among the treetops of mature fir forests in the Pacific Northwest, Townsend's Warbler also nests in montane spruce-fir (Picea-Abies) forests in Idaho, Montana, and northwest Wyoming, and in boreal forests in Alaska and the Yukon Territory. In September, it begins its southward migration to California and the highlands of Mexico and Central America, where it is the most common of all species (including residents) in some locales.
Townsend's Warbler was among the many species first collected by John Kirk Townsend during his expedition with Thomas Nuttall through the Rocky Mountains to the Pacific Coast in 1834. The description of Townsend's Warbler first appeared in the Journal of the Academy of Natural Sciences of Philadelphia in 1837 written by Nuttall under Townsend's name ( Mearns and Mearns 1992a ). The first specimen seems to have been procured in the forests along the Columbia River near Fort Vancouver, Washington.
On its breeding grounds, this warbler consumes insects gleaned from foliage, but on its Mexican and Central American wintering grounds it often exploits honeydew excreted by sap-sucking insects. Townsend's Warbler is most closely related to the Hermit Warbler (D. occidentalis) within a group also including Black-throated Green (Dendroica virens) and Golden-cheeked (D. chrysoparia) warblers. The ranges of the Hermit and Townsend's warblers overlap in Washington and Oregon, where they frequently hybridize ( Pearson 1997 ).
A. Sprunt ( Sprunt 1957a : 135) wrote, “The Townsend's [warbler] is one of the lesser known warblers.” Unfortunately, the statement is still true. With the exception of recent studies of winter species interactions (Hutto Hutto 1980 , Hutto 1987 , Hutto 1992 ) and breeding biology ( Mannan et al. 1983 , Matsuoka et al. 1997b ), most information on the life history of the Townsend's Warbler is anecdotal or consists of isolated observations. Community studies of breeding birds in old forests of the Pacific Northwest ( Ruggiero et al. 1991a ) and of migrants in Central America ( Hutto 1992 ) have provided valuable information. More recently, several investigations have focused directly on Townsend's Warbler, examining its habitat associations and breeding biology in Alaska ( Matsuoka et al. 1997a , Matsuoka et al. 1997b ) and its relationship with the closely related Hermit Warbler (D. occidentalis) in the Cascade Mountains of Washington ( Morrison and Hardy 1983a ).