the black-capped vireo , vireo atricapilla , is a small bird native to the united states and mexico .
it has been listed as an endangered species in the united states since 1987. the iucn lists the species as vulnerable .
the black-capped vireo is a songbird about 12 cm (4.5 inches ) in length .
sexually mature males are olive green above and white below with faint yellow flanks .
the crown and upper half of the head is black with a partial white eye-ring and lores .
the iris is brownish-red and the bill is black .
females are duller in color than males and have a slate gray crown and underparts washed with greenish yellow .
first year males are intermediate in coloration between adult males and females .
the male and female in a pair assist in nest construction and incubation .
the female broods the young , while the male supplies most of the food during the nestling phase .
typically , three or four eggs are laid .
the incubation period is 14 to 17 days , and the nestling period is 10 to 12 days .
breeding pairs are capable of producing more than one clutch per breeding season .
the male cares for some or all of the fledglings , while the female re-nests - sometimes with another male .
these birds are insectivorous , with beetles and caterpillars making up a large part of the diet .
black-capped vireos nest in "shinnery ," brushy areas with scattered trees .
shinneries primarily consist of shin oak or sumac .
appropriate height and density are important factors for this species' breeding success .
junipers seem to be of little or no importance .
foliage that extends to ground level is the most important requirement for nesting .
most nests are between 15 and 50 inches (35125 cm) above ground level and are screened from view by foliage .
territories are sometimes located on steep slopes , where trees are often clumped and intermediate in height .
on level terrain , preferred black-capped vireo habitat is a mixture of shrubs and smaller trees that average from eight to 10 feet high (2.5-3.5 m) .
black-capped vireos will no longer use sites where many trees are nearing full size .
the historic breeding distribution of the black-capped vireo extended south from south-central kansas through central oklahoma and texas to central coahuila , mexico .
at present , the range extends from oklahoma south through the edwards plateau and big bend national park , texas , to at least the sierra madera in central coahuila , mexico .
in oklahoma , the black-capped vireo is found only in blaine , cleveland , and comanche counties .
the winter range of this vireo is not well known .
it is thought to winter along the west coast of mexico from southern sonora to guerrero .
the black-capped vireo is threatened by brown-headed cowbird (molothrus ater) brood parasitism , human disturbance , and loss of habitat to urbanization , fire exclusion , grazing , and brush control .
