Bird of the Month: Black-throated Gray Warbler
By Andy McCormick
PC: Ollie Oliver (Black-throated Gray Warbler)
Scientific Name: Dendroica nigrescens
Length 5 in
Wingspan 7.75 in
Weight 10.29 oz
AOU Band code BTGW
The Black-throated Gray Warbler is a specialty species of the western United States and British Columbia. Its bold black and white coloration gives it a unique look among western warblers and makes it fairly easy to identify. It is gray above and white below with a black throat and cheek patch and dramatic white eyebrow (supercilium) and mustache (malar) stripes. It has a tiny yellow spot between the eye and bill. The female is lighter in color with gray replacing the black of the male. The song is buzzy and similar to the Townsend’s Warbler but with an inflected ending, such as zee-zee-zee-zee-bzz-zee or, buzz-see buzz-see buzz-see-buzz-see–wueeo (Dunn and Garrett).
This species of warbler is part of the super species virens complex formed around the Black-throated Green Warbler that also includes the Golden Cheeked, Townsend’s and Hermit Warblers. All five of these species share a black throat, white on the tail feathers, and white wing bars. All belong to the genus Dendroica, tree dwelling, from the Greek dendron, a tree, and oikos, a house or any dwelling place. The species name is from the Latin nigrescere, to become dark in color, in reference to its black and gray coloration (Holloway).
The Black-throated Gray is a medium-distance Neotropical migrant that winters in the very south of California, in Baja California Sur, and in the interior of central Mexico (Guzy & Lowther). It returns to Washington in late April to early May. In the southern portion of its range it prefers open mixed or coniferous woodland with brushy undergrowth. In the northern portion it prefers the middle to lower level of coniferous forests leaving the forest canopy to other warblers.
It nests on the extreme ends of branches of Douglas and other fir and juniper trees usually between 8 and 40 feet from the ground. At times the nest can be even lower. The neat cup nest is made of weeds and dry grass and is lined with feathers, fur, hair and moss. Typically, four creamy white eggs with brown spots are deposited. The Black-throated Gray Warbler has not been studied well and many aspects of its breeding biology including the incubation period and time to first flight are not known (Kaufman). It feeds on insects and is particularly fond of small green caterpillars in oaks and firs. It will also fly out to capture flying insects.
The species is fairly common and it is apparently not bothered by human activity. The population appears to be stable and it is protected under the Neotropical Migratory Bird Conservation Act, a cooperative agreement among Canada, Mexico and the United States. It does however seem that deforestation in both its breeding and wintering areas poses some risk to this species (Dunn & Garret).