Distribution: The breeding range of the black-throated gray warbler, Dendroica nigrescens, lies within the western United States and southern British Columbia, including Vancouver Island. Preferred breeding habitat includes dry oak slopes, pinyon woodlands, juniper woodlands, pinyon-juniper woodlands, open mixed woodlands, chaparral, and dry coniferous and mixed woodlands with a brushy under story. The black-throated gray warbler winters primarily in Mexico. It is found singly or in small groups in winter mainly in dry, open woodlands and tall scrub. The black-throated gray warbler occur statewide in Utah as a common summer resident.
Ecology: Little detailed migration data are available. Likely the black-throated gray warbler is a short- to long-distance nocturnal migrant that apparently joins and migrates with mixed species flocks. Typically individuals leave the breeding grounds by late August to early September. Return migration begins in early March. Birds arrive on the breeding grounds in Utah by late April to early May. Black-throated gray warblers use a variety of semi-open habitats on migration, especially riparian areas.
The black-throated gray warbler is a single brood species that begins its breeding cycle in early to mid-May. The nest is probably built by both sexes and consists of a well-defined cup lined with hair and grasses that is placed 1 - 3 m out from the trunk of a tree or shrub. Usual clutch size is 4 eggs (range 3-5). Only the female develops a brood patch, so incubation likely is carried out by the female alone. Young are altricial and tended by both parents (Baicich and Harrison 1997; Kaufman 1996; Curson et al. 1994; Bent 1953).
Habitat Requirements: In addition to the habitat preferences listed above, the black-throated gray warbler typically breeds in pinyon-juniper communities in Utah. The species prefers densely wooded areas over areas where trees are more widely spaced; open areas are extensively used for foraging.