This elegant but little-studied warbler of western North America is a relatively common bird of piñon-juniper, pine, and mixed oak-pine forests. Found and first described by John Kirk Townsend (Townsend 1837) near Ft. William (now Portland), Oregon, the Black-throated Gray Warbler was already known there as “Ah Kah a qual” by the Chinook (J. K. Townsend, in Audubon 1839b). It breeds generally west of the Rocky Mountains from northern Mexico to British Columbia, and winters mostly in Mexico. It is a short-to medium-distance Neotropical migrant and, like many such migrants, is insectivorous. Unlike some other Neotropical migrants, Black-throated Gray Warbler populations do not seem to have been affected by human activities to any great extent, but changes are difficult to assess because so little is known about this species.
This bird tends to be relatively tame and is often readily observed at close quarters as it forages methodically among foliage. Nevertheless, little is known about many aspects of its natural history. Although its nests are not unusually hard to find and are often placed low enough to be observed easily, almost no information is available on the breeding biology of this species. The only intensive studies of this warbler have dealt with foraging (e.g., Keane 1991) and song (e.g., Morrison 1990).
Recent genetic studies found that the genus Dendroica, in which S. nigrescens was placed formerly, was paraphyletic with Wilsonia citrina (the Hooded Warbler) and S. ruticilla (the American Redstart). As a result, all of the many species of Dendroica warbler, as well as W. citrina, were merged into the genus Setophaga (Chesser et al. 2011), the older name and a genus that for many decades was thought to be monotypic.