Black Capped Vireo (Vireo atricapilla)
(Federally listed as Endangered)
Description: This is a small songbird approximately five inches
in length. The back, wings and sides are a greenish color, and
the head is either black (in males) or gray (in females). The
breast and belly are white, and there are white markings around
the eyes and above the bill that look like spectacles.
Black-capped Vireos feed primarily on soft-bodied insects,
especially caterpillars, that they glean off of leaves and
twigs.
Habitat: Black-capped Vireos are typically found in low brushy
thickets comprised of deciduous trees such as oaks, redbuds and
plums. These thickets are often found on thin and rocky soils
that slow or stunt the growth of trees and maintain the low
thickets that the vireo prefers. Periodic fires and drought are
important in maintaining this scrubby habitat. Black-capped
Vireos are migratory and occur in Oklahoma between mid-April and
early September. Vireos form breeding pairs shortly after
returning to Oklahoma and their nesting season begins in the
first week of May and continues through mid July. Vireos lay
their eggs in small hanging nests that are normally constructed
at the end of a branch and commonly hidden by overhanging
leaves. Nests are usually built only four to eight feet above
the ground, and vireos lay an average of four eggs. Most pairs
of vireos raise one brood of chicks per year, although a small
percentage may rear two broods.
Current and Historic Distribution: Currently, there are only two
known populations of Black-capped Vireos in Oklahoma. One
population is large (over 2,000 birds) and is located in the
Wichita Mountains of northern Comanche County. The other
population is small (less than 30 birds) and is located in the
canyon lands of northern Blaine County north of Watonga.
Historically this species was once more widespread in central
Oklahoma and was found in scattered locations in the Cross
Timbers region of the state. Nesting populations also remain in
portions of northern Mexico and central Texas including the
Edward’s Plateau. During the fall, all Black-capped Vireos in
Oklahoma and Texas migrate south to spend the winter in southern
and western Mexico.
Reasons for Decline: Vireo populations have declined for several
reasons including the loss and modification of their nesting
habitat. Much of their oak scrub habitat has been cleared and
converted to cropland or non-native pastureland. The condition
of most of their remaining habitat has declined as a result of
fire suppression which has allowed the encroachment of taller
vegetation such as Eastern Redcedar. Nest parasitism by the
Brown-headed Cowbird is another contributing factor. The
Brown-headed Cowbird lays its eggs in the nests of songbirds
such as vireos, and in the case of the Black-capped Vireo the
young cowbirds hatch sooner and are larger than the young vireos
so they typically cause the deaths of all of the vireo chicks in
the nest. Brown-headed Cowbird populations have increased over
the past century as a result of changes in the populations of
large grazing animals in the U.S.
County by County List of Endangered and Threatened Species
US Fish and Wildlife Endangered Species Lists