BIRD OF THE WEEK: August 21, 2015
SCIENTIFIC NAME: Vireo atricapilla
POPULATION: 20,000 individuals
HABITAT: Breeds in fire-maintained scrub-oak habitats in Texas, Oklahoma, and northern Mexico; winters in dry scrub in western Mexico
The smallest vireo occurring regularly in the United States, the Black-capped Vireo has been largely extirpated from its traditional breeding range in arid, fire-adapted scrublands — habitat it shares with other Watch List species such as Varied Bunting. The species was federally listed as Endangered in 1987; in late 2016, it was proposed for delisting due to recovery of habitat and reduction of threats.
This is a species of low scrublands found in Oklahoma, Texas, and northern Mexico. To nest successfully, Black-capped Vireos require a mixture of scrubby deciduous thickets with some trees and open ground. This habitat has become harder to find, especially in the rapidly developing Edwards Plateau of Texas. (However, there is good news from Fort Hood, where the vireo and Golden-cheeked Warbler both appear to be thriving.)
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Habitat loss, fire suppression, cowbird parasitism, and unsustainable livestock grazing are the chief factors that have contributed to this species' steep decline. Nest predation by invasive species, such as feral cats and fire ants, pose an additional threat.
Like other vireos, the Black-capped feeds primarily on insects, gleaning them from foliage with its hook-tipped bill as it moves through the branches.
The species is notably different from other vireos in two key ways. The Black-capped is the only vireo that is sexually dimorphic—females have a gray head and males a black head—and it's the only vireo species that requires two years for males to attain breeding plumage.
Both sexes help to build the nest and incubate the eggs, sometimes 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.
Cowbird management and prescribed burns on public lands within the Black-capped Vireo's breeding range have led to local population increases at Balcones Canyonlands National Wildlife Refuge, Fort Hood, and Kerr Wildlife Management Area.
On private lands, conservation has been encouraged through programs including the Texas Parks and Wildlife Department's Wildlife Management Plans and Landowner Incentive Program.
It's an important species for ABC, too. As part of our Migratory Birds initiative, which aims to protect birds throughout their full life cycles, we're working to preserve the Mexican thorn scrub region that serves as winter habitat for the Black-capped Vireo as well as Elf Owl, Rufous Hummingbird, and Painted Bunting.
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