Black-throated Gray Warbler
|Black-throated Gray Warbler|
Sylvia nigrescens Townsend, 1837
The Black-throated Gray Warbler (Setophaga nigrescens) is a songbird of the New World warbler family. It is 13 cm (5 in) long and has black, gray, and white plumage. It breeds in western North America from British Columbia to New Mexico, and winters in Mexico and the southwestern United States. Common in its forest habitats, it does not seem to be seriously threatened by human activities, unlike many migratory warblers.
The Black-throated Gray Warbler has mostly black, gray, and white plumage, which is soft, lacking gloss. With its striping and the small yellow spot between its eye and bill, it is a distinctive bird. The sexes differ slightly, both having gray upperparts with black streaks, and white underparts with black streaks on the flanks. The adult male is striped on its head, with a black crown, throat, and stripe below the eye, and white around its chin and above its eye. The adult female has more dingy plumage on its head, with a white throat and dark gray cheeks. The most similar birds to the Black-throated Gray Warbler are the Black-and-white and Blackpoll Warblers, which although black have entirely different patterns.
It is typically 13 cm (5 in) long, weighing 8.4 g (0.29 oz). Wing lengths are 5.6–6.9 cm (2.2–2.7 in), tail lengths 4.7–5.5 cm (1.9–2.2 in), bill lengths 8.4–9.6 cm (3.3–3.8 in), and tarsus lengths 1.66–1.88 cm (0.65–0.74 in), with females slightly smaller than males.
This bird gives a sharp tup or thick call, like that of Townsend's Warbler but flat and unmusical, as well as a high see flight call. The male's song is a series of buzzy notes, with the earlier notes doubled and the next to last note high. This song has three variations, including a quiet "soft song" given by the males while following females gathering material for a nest.
The Black-throated Gray Warbler was first described by John Kirk Townsend from a specimen collected near today's Portland, Oregon. It was known to the Chinook inhabitants of the northwest coast, who called it Ah Kah a qual. Townsend described the species as Sylvia nigrescens, placing it with the other New World warblers and the unrelated Old World warblers in the genus Sylvia. It is now placed in the genus Dendroica, along with about thirty other species. Within this genus, it is part of a group with black throats and yellow face markings that includes the Hermit Warbler and Townsend's Warbler. Among these species, it is usually considered an early offshoot, but genetic studies suggest a close relation to Grace's Warbler.
Of these relatives, Townsend's Warbler and the Hermit Warbler overlap with the Black-throated Gray Warbler, but inhabit different habitats. While these two species hybridize commonly, records of hybridization with the Black-throated Gray Warbler are uncommon.
There are two subspecies, which are highly similar and of dubious validity. The nominate subspecies D. n. nigrescens occurs on the Pacific coastal region from British Columbia to northern California, while D. n. halseii, described by Giraud in 1841, occupies the remainder of its range. D. n. halseii birds are slightly larger and more gray in their upperparts.
Distribution and habitat
The Black-throated Gray Warbler breeds in western North America, its range extending from southwestern British Columbia along the Pacific coast, and east to New Mexico and southern Montana. It winters mostly in Mexico, from southern Baja California to Oaxaca state. It has spread into parts of Wyoming and Montana only recently, as Juniperus osteosperma has expanded its range due to a warming climate. Vagrants have been recorded across eastern North America. It breeds in open coniferous and mixed forest with a brushy understory, in dry open oak forests, and in chaparral and other scrubland. It is particularly associated with pinyon pines, junipers, and oaks. It migrates to the south late in the fall, returning north in mid-spring. While migrating, it forages in any woodland or scrub it passes through. In its wintering grounds, it occurs in dry woodland and tall scrub. Though its status is not well known, it does not appear to be seriously threatened by habitat destruction or other human activities, unlike many migratory warblers. It is a fairly common bird, among the most common in some localities. Because of its commonality, it is assessed as Least Concern on the IUCN Red List.
The Black-throated Gray Warbler is usually approachable, and can easily be observed while foraging. Despite this, it is poorly known, especially in its breeding behavior, of which Birds of North America said "almost no information is available". It forages, often in flocks with other species. It feeds on insects gleaned on low branches, especially caterpillars.
The nest is usually placed on a horizontal tree branch or in a shrub, a few metres above the ground. The nest is an open cup constructed of grass stalks and other fibres, and lined with feathers and hair. The female lays 3–5 pinkish eggs with brown dots from May to July. Incubation and fledgeing periods are not recorded. It has been recorded giving a distraction display, pretending to be injured to distract predators from its nest. Both parents feed the young, though the female may do so more frequently.
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