Black-throated Gray Warbler

The Black-throated Gray Warbler is a warbler of the North American west and is a short-to-medium distance Neotropical migrant. It breeds generally west of the Rocky Mountains from northern Mexico to British Columbia and winters in central and southern Mexico. First arrivals in southwestern B.C. are usually during the second week of April.

Adult Male (spring/summer)

Black crown, chin and throat; white supercilium, black auricular, white submoustachial stripe and yellow supraloral mark; upper parts blue-gray with some fine black streaking; white center of breast with black-streaked flanks; two white wing bars, white vent and undertail coverts.

Adult Female (spring/summer)

Similar to adult male but black of the head not as dark. Chin variably mottled with black throat and black upper breast band. Yellow supraloral mark not as bright yellow as on males.

Juvenile

Black of crown mostly restricted to sides, center of crown gray; auriculars gray; yellow supraloral mark dull yellow; white throat, sometimes with black steaks or flecks and fine streaking on back absent or dull.

General:

This is an averaged sized foliage-gleaning wood warbler. Length: 12-13cm. Wing: 23-24cm. Weight: 12.3grams.

Behaviour:

The Black-throated Gray warbler tends to be relatively tame and is often readily observed at close quarters as it forages methodically among foliage. It forages deliberately gleaning and reaching, with occasional hover gleaning and short sallies for insects.

Habitat:

Common in a great variety of woodlands throughout its range, it is home in a wide variety of semi-arid deciduous and conifer woodlands of the western U.S. and southwestern B.C. Most foraging is at mid-level within the canopy.

Information:

The Black-throated Gray is an elegant warbler and was first described by John Kirk Townsend near Ft. William (Portland), Oregon. It was already know there as “Ah Kah a Qual” by the Chinook. Little is known about many aspects of its natural history. The nest is a deep, compact cup of plant fibers and grasses, bound with spider webs and lined with fir, feathers, and hair. Nests are often placed low (3-10ft.) in bushes, but frequently are placed at 20ft. or more, well out on conifer limbs. There are usually 4 white or cream-white, speckled brown eggs.

Similar species:

Conservation Status:

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. Listed as Least Concern.

Capture Rates

The Black-throated Grey Warbler’s preferred habitat is open coniferous or mixed coniferous-deciduous woodland, therefore not seen in high numbers around our banding station. Captures generally begin in July and continue through October when activity picks up as juveniles disperse and prepare for their relatively short migration southward.

Molt Summary:

PF: HY partial (May – Aug), PB: AHY complete (July-Aug). PBs occur on the summer grounds.

Preformative often includes all med and gr covs and often the greater alula. No terts or rects.

PA: Limited to the head feathers and may be continuous from Oct – Apr.

Juveniles are brownish yellow, often with streaks in the upperparts, and have buffy brown wingbars. Most juveniles can be sexed by the colour of the flight feathers and amount of white in then outer rects (r6).

Juveniles like this HY in July show duller, brownish washed upperparts and all the characteristics of birds in juvenal plumage such as prominent gapes, loosely textured feathers (particularly nape and undertail coverts) and obvious natal plumes.

This HY male (left) and female (right) illustrate the sexual dimorphism in this species. HY males have blackish crowns and auriculars, black mottled throats and black streaking to the sides of the breast whereas females have gray crowns and auriculars, whitish throats and only feint blackish spotting to the sides of the breast.

Hatch Year (HY) male in August. First year males can be separated from first year females by the mixed gray and black (rather than grayish) crown and auriculars, distinct black centers to the back feathers and median coverts with white tips usually without black shaft streaks.

The photo below shows the wing of the HY male above following completion of its preformative molt having replaced all lesser, median, greater coverts, carpal covert and greater alula covert, the molt limit between replaced outer greater coverts and retained primary coverts and between the greater alula covert (A1) and lower alula feather (A2) .

Note the median coverts of this HY male with white tips without black shaft streaks.

Tail shape is not reliable for ageing Setophaga warblers as all age classes can show rounded rectrices.

The photo below is of the HY male immediately above showing extensive white in the outer rectrices (R4-R6). The amount of white should be used with caution when separating sexes as the Interior (halseii) subspecies generally shows more white than is normal in the coastal subspecies (nigrescens).

The photo below shows another HY male in August following completion of its preformative molt having replaced all lesser, median, greater coverts, carpal covert and greater alula covert, the larger red arrow pointing to the molt limit between replaced outer greater coverts and retained primary coverts and the smaller red arrow pointing to the molt limit between the greater alula covert (A1) and lower alula feather (A2) .

Compare the median coverts of this HY male with the first year (HY/SY) females below.

This HY male in August is showing a similar pattern of replaced and retained feathers having replaced lesser, median, greater coverts, the carpal covert and greater alula covert (A1), the molt limits indicated with red arrows between the outer GC and inner PC and between the greater alula covert (A1) and lower main alula feather (A2).

Again, notice the median coverts with white tips without black shaft streaks.

Contrast the median coverts of the HY males above with those of this HY female in August showing a similar pattern of retained and replaced coverts but with obvious black shaft streaks to the median coverts (blue arrow).

These two photos both show tails of HY males in August and both show extensive white in the outer rectrices (R4-R6). Again, the amount of white should be used with caution when separating sexes as the Interior (halseii) subspecies generally shows more white than is normal in the coastal subspecies (nigrescens).

This HY female tail in August is also showing extensive white to the outer rectrices (R4-R6) illustrating that caution should be used when separating sexes based on this characteristic alone but notice the grayish brown colour of the rectrices of the female compared with the darker blackish rectrices of the males above. Also notice the moderately large and distinct black centre of the single, visible uppertail covert in the top photo of the male above versus the indistinct, narrow dusky centre of the single, visible uppertail covert of the female below.

Unlike many of the Setophaga warblers BTYW often have a very limited prealternate molt limited to head feathers.

The photo below is of an SY female in June. In its preformative molt after the breeding season in the previous year this bird replaced all lesser and median coverts, the carpal covert and greater alula covert but only some outer greater coverts, the preformative molt limit between the outer greater covert and inner primary covert indicated by the red arrow. The green arrow points to the retained juvenal inner greater coverts. In its 1st prealternate molt in the current year this bird replaced a single inner greater covert (GC 7), the glossy black feather indicated by the blue arrow (this feather may or may not have also been replaced in the PF).

Again notice the white tips and small shaft streaks of the median coverts diagnostic of first year (HY/SY) females (white arrow) and compare these to the HY males above.

This ASY female in June is showing relatively fresh and dusky primary coverts not contrasting markedly in colour or wear with the greater coverts. Notice the blackish lower main alula feathers (A2 & A3) not contrasting with the greater alula covert (A1) and white tips to the median coverts with small shaft streaks.