Bird of the Month - April 2003
 

Black-throated Gray Warbler
Dendroica nigrescens

by David Fix

Think of North American warblers, and an image of color may sweep across your mind.  Maybe a green back, yellow breast... perhaps some blue or rich brown.  Many of the most highly colorful warblers are species in the great treetop genus Dendroica.  Yet here in the Redwood Region we enjoy the sight of a widespread western Dendroica--typical in other respects--which lacks conspicuous color and is simply black and white or gray and white. This is the Black-throated Gray Warbler.

While it may lack the eye-catching colors of its close relatives the Hermit and Townsend’s warblers, the Black-throated Gray makes it all up in spirit.  These birds generally avoid closed-canopy conifer forests, instead preferring more broken, uneven-aged, or park-like stands in which oaks are strongly represented.  Hillside or ridgeline regrowth timber at lower and middle elevations dominated by tanoak, canyon live-oak, black or white oak, and with only a modest conifer component attract them.  They also differ from Hermit and Townsend’s warblers in spending a great deal of time foraging not in the taller treetops but within the welter of lower limbs created by the mingling of taller shrubs, struggling understory trees, and the lower and middle canopy of whatever conifer trees may be present in a given territory.  This habit, together with the species’ propensity for quick response to ‘spishing’ or pygmy-owl imitations, causes it to be among the more consistently visible and engaging warblers.

This species appears in migration in early to mid-April, quickly becoming numerous across the drier slopes and ridges east of the coastal fog belt and locally westward.  By early May, the songs of males and soft contact notes of females may be readily detected in the ‘morning chorus’ from the bottoms of river canyons upslope through the oak-and-Douglas-fir woods to the ridgelines.  Where extensive stands of larger, vigorous conifers have outcompeted oaks and have formed a deep-woods setting, ‘BTGs’ give way to Hermit Warblers.  Even in post-breeding dispersal and during migration, these warblers are seldom met with at higher elevations.  In our area, they are far more common even a few miles inland than along or near the coast.

Nesting takes place in May, June, and the first half of July.  The cup-shaped, feather-lined nest is usually built in lower limbs of oaks or conifers but may be as high as 50 ft. above ground.  Three to five eggs are laid.  Only one brood is known to be raised per year.  Frequency of the buzzy, emphatic song diminishes sharply as nestlings approach fledging. Migration is in full swing by August and few are seen later than September, although late fall and early-winter stragglers may be noted along the coast or in interior valleys. Fall migrants in mixed-species flocks are easily overlooked.

Identification of Black-throated Gray Warblers is easy.  Males are black on crown, cheek, and throat and have a tiny bright yellow spot before the eye.  Females and young birds have the black of the face replaced by paler gray, and some have nearly white throats.  All have a few neat black streaks along the sides and two white wing-bars.  The rather similar Black-and-White Warbler is more strikingly streaked throughout, has black spots on the undertail coverts, and creeps along larger limbs rather than gleaning and flycatching amid slender twigs and foliage.