Wilson's Warbler

Common in Sonoma County during spring and autumn migration and over the summer, but little seen here in the winter months. Favors fairly dense woods near water (likes willows and alders), bogs and thickets near water, wooded edge environments near the coast and inland, and occasionally coniferous forest. Flits rapidly among the branches of trees and bushes gleaning insects, making it hard to get a good look at this bird, which never seems to sit still for more than an instant. Also hover-gleans and flycatches. In the spring, presence often recognized by song before the bird is seen (link below). Known to nest in appropriate habitat in most of Sonoma County except the southern extreme, near the Petaluma-area wetlands and San Pablo Bay. Named for pioneer ornithologist Alexander Wilson (active early 19th century). The American Ornithological Union moved this species from the genus Wilsonia to the genus Cardellina in July 2011. Older sources will call this bird Wilsonia pusilla.

Wilson's Warbler is one of our more distinctive warblers. Smaller than many warblers but with a proportionately long tail. Males are easily recognized by the black cap and beady black eyes that contrast sharply with the otherwise mostly yellow face and underparts. Yellow-olive back, wings, and tail. No wing bars or sometimes just a hint of wing bars. Comparatively thin, orange-tinged legs. Yellow is brightest on the face, especially above and in front of the eye. Many field guides show a variable olive auricular patch. Pacific Coast birds of the subspecies C. pusilla chryseola are the yellowest of the three main subspecies recognized and have the palest, least marked faces (in other words, they are least likely to have the olive patch) but show a slight orange tinge at the forehead. The bird in the photo above is chryseola. Females are similar to males but somewhat drabber in color and with a less developed black cap (at some angles, may appear almost capless). Female cap may be more olive than black and may be lacking entirely in immature females. Also reduced in first-fall males.

Wilson's Warbler may be confused with Yellow Warbler (Setophaga petechia) in that bird's duller plumages, but Yellow Warbler never has a black or dark cap and Yellow Warbler is yellow where Wilson's Warbler is yellow-olive.

Selected county sightings: Gracianna Winery, Westside Rd. (Jan 21, 2014, an unusual winter sighting, Colin Talcroft); Spring Lake (April 14, 2012, Colin Talcroft); Owl Canyon, Bodega Bay (April 7, 2012, Daniel Edelstein); Owl Canyon, Bodega Bay (October 26, 2011, Scott Carey); North End Bodega Harbor (October 17, 2011, Ruth Rudesill)

English synonyms: Blackcap, Black-cap Green Warbler, Black-capped Warbler, Green Black-capped Warbler, Pileolated Warbler, Wilson's Flycatcher

Wilson’s Warbler in other languages--German: Mönchswaldsänger, Mönchs-Waldsänger; Spanish: Bijirita de Wilson, Chipe Corona Negra, Chipe Coroninegro, Chipe de Coronilla Negra, Chipe de Wilson, Chipe pelucillo, Ciguíta de Wilson, Reinita de Wilson, Reinita Gorrinegra; French: Fauvette à calotte noire, Paruline à calotte noire, Sylvette à calotte noire; Dutch: Wilsons Zanger, Wilson-zanger; Russian: Вильсония малая, Вильсония-крошка, Малая вильсония; Chinese: 黑头威森莺; Japanese: ウィルソンアメリカムシクイ (uiruson amerikamushikui)

(Language information from Avibase, Birds of Europe (Mullarney et al, Princeton Field Guide Series), and Birds of Asia (Mark Brazil, Princeton Field Guide Series).