Balcones Canyonlands National Wildlife Refuge

Balcones Canyonlands National Wildlife Refuge is a national wildlife refuge in the Texas Hill Country northwest of Lago Vista, Texas. The refuge was established in 1992 to protect the habitat of two endangered songbirds, the golden-cheeked warbler and the black-capped vireo, as well as the habitat of countless other wildlife species in the Texas Hill Country. The refuge supplements the Balcones Canyonlands Preserve in Austin.

The refuge is situated in a heavily dissected area of the Edwards Plateau, which has numerous steep-banked streams and canyons. The canyons that face Austin were carved into the limestone of the Edwards Plateau by Colorado River tributaries.

An underground network of caverns, sinkholes, and springs lies beneath the Edwards Plateau’s surface. This underground realm is home to a variety of spiders, beetles, and other species that are peculiar to this region of Texas. The Edwards Aquifer, located even deeper beneath the surface, contains billions of gallons of water and provides drinking water to about one million people. The aquifer also serves as the source of many springs that feed Hill Country rivers, which eventually run into the marshes, estuaries, and bays of Texas’ Gulf Coast.

The Hill Country’s vegetation includes oaks, elms, and Ashe juniper trees (often referred to as “cedars” in Texas). The endangered golden-cheeked warbler and black-capped vireo rely on various stages of this vegetation’s succession. The warbler is the only bird that nests entirely on the Edwards Plateau.

Golden-cheeked warbler

The golden-cheeked warbler (Setophaga chrysoparia) is a critically endangered bird that breeds in Central Texas from Palo Pinto County southwestward along the eastern and southern edges of the Edwards Plateau to Kinney County. The golden-cheeked warbler is Texas’ sole indigenous bird species.

The golden-cheeked warbler has brilliant yellow cheeks that contrast with its black throat and back. It is also distinguished by the distinctive buzzing song that it emits from the wooded canyons where it breeds. Golden-cheeked warblers breed in 33 counties in central Texas and rely on ashe juniper (blueberry juniper or cedar) for fine bark strips used for nesting.

The golden-cheeked warbler can be found in several Texas state parks. Colorado Bend State Park (SP), Dinosaur Valley State Park (SP), Garner State Park (SP), Guadalupe River State Park (SP), Honey Creek State Natural Area (SNA), Hill Country SNA, Kerr Management Area, Longhorn Cavern SNA, Lost Maples SNA, Meridian SP, Pedernales Falls SP, Possum Kingdom SP, and South Llano River SP are among these parks.

The golden-cheeked warbler is a Texas and Mexico endemic. Their natural habitat varies from moist to dry places in central and southern Texas. In the more wet realms, nesting habitat can be found in tall, closed canopy, compacted, mature stands of ashe juniper trees, as well as Texas, shin, live, lacey, and post oak trees. Golden-cheeked warblers are found in upland juniper-oak forests off flat topography in Texas’ drier regions. Their nests are made of ashe juniper bark and spider webs. Females give birth to three to four eggs. When migration and winter arrive, the habitat remains consistent: a range of short-lived evergreen woods with pines ranging in elevation from 3,300 to 8,300 feet.

Black-capped vireo

The black-capped vireo (Vireo atricapilla) is a tiny bird that is native to North America and Mexico. In the United States, it was designated as an endangered species in 1987. The black-capped vireo was delisted in 2018 as a result of successful conservation efforts on the US Army’s Fort Hood and Fort Sill. The species is listed as vulnerable by the IUCN.

The black-capped vireo is a songbird that measures approximately 12 cm (4.5 inches). Males with sexual maturity are olive green on top and white on the bottom, with slight yellow flanks. The crown and upper half of the head are black, with a white lores and a partial white eye ring. The bill is black, and the iris is brownish-red. Females are paler in color than males, having a slate-gray crown and greenish yellow underparts. First-year males have more gray in their caps than adult females.

The black-capped vireo’s ancient breeding range stretched south from south-central Kansas through central Oklahoma and Texas to central Coahuila, Mexico. Currently, the range runs south from Oklahoma, via the Edwards Plateau and Big Bend National Park in Texas, to at least the Sierra Madera in central Coahuila, Mexico. The black-capped vireo is exclusively found in Blaine, Cleveland, Cotton, and Comanche Counties in Oklahoma. It is unknown where this vireo spends the winter. It is supposed to spend the winter on Mexico’s west coast, from southern Sonora to Guerrero.

Brown-headed cowbird (Molothrus ater) brood parasitism, human disturbance, and habitat loss due to urbanization, fire exclusion, grazing, and brush clearance are all threats to the black-capped vireo. The species is now controlled by the Texas Parks and Wildlife Department and the Oklahoma Department of Conservation, with population estimates in the tens of thousands. The US Army’s conservation efforts are continuing to improve the conservation status of the black-capped vireo.

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