Associated Species: Other species that may use habitat in a similar way and/or respond similarly to threats, management, and conservation activities include Ash-throated Flycatcher, Mountain Chickadee, Juniper Titmouse, White-breasted Nuthatch, Bewick's Wren, and Chipping Sparrow.

Distribution: Black-throated Gray Warblers have two nesting season ranges, the first in Pacific coastal areas from southwestern British Columbia south sparingly to northern Baja California, and the second in the Intermountain West from central Oregon, the southern fringe of Idaho, and southwestern Wyoming to southeastern Arizona, adjacent Mexico, and southern New Mexico. These warblers winter from coastal southern California and southern Arizona south through the highlands of Mexico and casually to Guatemala (AOU 1983, DeGraaf and Rappole 1995). They are fairly common summer residents in pinyon-juniper woodlands across the southwestern half of Colorado. Some surveys show these warblers to be the most frequently encountered birds in the pinyon-juniper woodland (BLM unpublished records). They are rare in the ring of pinyon-juniper around the San Luis Valley. In migration they are casual on the eastern plains of Colorado to the Kansas state line (Andrews and Righter 1992).

Habitat Requirements: Black-throated Gray Warblers, in Colorado, are pinyon-juniper obligates, preferring tall, dense pinyon-juniper woodlands (Andrews and Righter 1992). They also occasionally use other conifer types adjacent to pinyon-juniper, such as ponderosa pine and Douglas-fir. Although there are few controlled data, the density of Black-throated Gray Warblers in small tracts (<16 ha; <40 ac) appears to be just as high as it is in large acreages (BLM unpublished data). Small tracts isolated by more than 8 km (5 mi) may have sparser populations than those less than 8 km (5 mi) from larger stands. In a one-year data set, these warblers and the White-breasted Nuthatch showed a preference for pinyon-juniper stands with little understory. This may be due to their preference for stands of larger, taller trees, which typically will have out-competed most of the understory shrubs. Black-throated Gray Warblers selected for stands of pinyon pine dominance over juniper. Pinyon pine tends to dominate on higher elevation, wetter sites, where trees grow taller. Selection for pinyon pine dominance was also observed with White-breasted Nuthatches, Mountain Chickadees, Clark's Nutcrackers, and Hermit Thrushes. In the Southwest and Pacific states, these warblers are consistently associated with oaks in the habitat mix. Gambel oak is almost always associated with upper elevation pinyon-juniper, but Gambel oak has yet to be associated with the occurrence of Black-throated Gray Warblers in the Intermountain West.

Ecology: Black-throated Gray Warblers are pinyon-juniper woodland obligates in their Intermountain breeding range. This obligation may weaken in southeastern Arizona, but in Colorado it is strong. In mid April, the birds return from their shrubby winter ranges to the pinyon-juniper stands and begin tentatively to sing. By the second week of May the males are on territory singing strongly. They generally begin to lay eggs in late May. The young hatch in June and most have left the nest before the end of that month. The nest is built in the low to mid canopy of a tree on a horizontal limb. The nest is built with juniper bark shreds, bits of cocoons, dry leaves, plant down, and hair, and always has feathers woven into the interior lining. These materials are neatly held together and to twigs with spider webs (Harrison 1979). Summer foods are almost wholly insects. Black-throated Gray Warblers are foliage feeders. Black-throated Gray Warblers are inquisitive and tolerate at least temporary human presence well. This species may be vital in the control of pine and pinyon needle scales, juniper scales, leaf miners, oak lace bugs, fruitworm caterpillars, and tree crickets among other potential pests (Furniss and Carolin 1977). In pinyon-juniper woodlands in the White and Inyo mountains of California, pinyon pines were used more than junipers after mid June. Males foraged higher on average than females and spent more time working twigs and branches, while females searched foliage more (Keane 1991 in Guzy and Lowther 1997). Cowbird parasitism is apparently low (Bent 1953). Two of three parasitized nests in California had layers of new flooring laid over the cowbird eggs (Guzy and Lowther 1997). Predation by jays and snakes is apparently often high (Bent 1953).

Management Issues and Conservation Recommendations: Black-throated Gray Warblers serve as indicators of healthy pinyon-juniper woodland. Monitor for significant changes that could identify problems in either its summer or winter ranges.

Status and Reasons for Concern: The Colorado and Physiographic Area 87 overall priority scores are relatively high (21) for this species. Within Physiographic Area 87, BBS data do not show a statistically significant annual rate of change between 1969 and 1996 (P = 0.35, n = 14 routes). Black-throated Gray Warblers were present on an average of 39.56% (SE = 3.73) of the BBS routes run in Physiographic Area 87 in Colorado during 1988-1997, at an average abundance of 1.16 (SE = 0.22) individuals per route. Mean number of routes run in Physiographic Area 87 during 1988-1997 was 11.4 (SE = 1.55). This species is monitored by MCB with point transects.

Biological Objective: Maintain the species' distribution and abundance, based upon results of the BBS and MCB monitoring programs. A MCB pinyon-juniper woodland point count average of 0.3 or better occurrence rate per point would indicate good population densities.

Selected References: Andrews and Righter 1992, AOU 1983, Bent 1953, DeGraaf and Rappole 1995, Furniss and Carolin 1977, Guzy and Lowther 1997, Harrison 1979, Kingery 1998.