SCIENTIFIC NAME: Vireo bellii
The Black-capped Vireo is one of the smaller vireos seen in North America. It is mostly found in southern Texas and into Mexico.
It is an endangered bird species. Its decline is thought to be caused by parasitism by the cowbirds, which lays their own eggs in the vireo's nest.
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.
Females and immatures are less vividly colored overall.
First year males often (but do not always) have more extensive gray in the cap, similar to adult females.
The Black-capped Vireo measures about 4.3 inches in length, with a wingspan of 7.1 inches. They weigh about 8 to 10 grams.
SONGS: Sings an incessant string of rapid, twittering 2- and 3-note phrases, rising and falling in tone, with a remarkable variation.
CALL: A rapid “jidit” is the most commonly heard call, amazingly similar to the call of Ruby-crowned Kinglet.
OTHER SOUNDS: Agitated birds may snap the bill loudly.
They feed mostly on insects and spiders, particularly during the summer breeding season. They may also feed on small berries, particularly during the winter.
They are found in a variety of brushy habitats, including chaparral, pinyon-juniper shrublands, and arid thorn scrublands.
Restricted to a small area in North America. There is a small population in Oklahoma, and the largest numbers are found in central regions of Texas. These vireos also have a breeding range in Mexico. They spend their winters along Mexico's Pacific coast.
Both sexes build an open cup-shaped nest made of leaves, grasses, plant fibers, and plant down, lined with grasses and camouflaged with paper, string, snake skin, feathers, spider cocoons, and other oddments. But the female does most of the work.
Typically, the female lays 3 or 4 eggs.
The incubation period is 14 to 17 days, and the nestling period is 10 to 12 days.