Wilsonia pusilla
(Wilson's Warbler)

Physical Description:
4 1/2-4 3/4" (11-12 cm). Black crown; yellow below and on head and nape; olive-green back and wings; dark eyes. Females have duller crown.

Similar Species- Female Yellow Warbler

Song:
A short, chattering trill, dropping in pitch.

Distribution:
Breeds from portions of Alaska and Canada, south to southern California, central Nevada, northern Utah, northern New Mexico, northern Minnesota, and portions of upper New England. Winters occasionally along Gulf Coast and southern Texas, throughout most of Mexico, and commonly in Central America.

Diet:
Feeds on insects such as wasps, ants, flies, beetles, and caterpillars.

Ecology:
Builds nest on ground. Forages throughout available vegetation, obtaining most food from leaves by gleaning while perched or flying. Usually solitary and territorial in winter, but may join mixed flocks. California study found territory size in different habitats ranged from about 0.2-2.2 ha.

Reproduction:
clutch size is commonly 3-4 eggs in coastal California, 4-5 in Sierra Nevada, and 5-6 in Alaska. Incubation lasts about 12-15 days; female incubates eggs. Young are tended by both parents, and leave nest at 9-10 days (California). In Sierra Nevada, some males are polygynous.

Conservation:

Element Code:	ABPBX16020
Status:	Protected nongame species
Global Rank:	G5
State Rank:	S5,NTMB
National Rank:	N5B

Important State References:
Douglas, D.C., J.T. Ratti, R.A. Black, and J.R. Alldredge. 1992. Avian habitat associations in riparian zones of Idaho's Centennial Mountains. Wilson Bull. 104:485-500.