You’re listening to Centex Sustains. I’m your host Christine with the Cen-Tex Sustainable Communities Partnership.

We will highlight an article by David Cimprich a Fort Hood biologist who shares how Fort Hood has help recover the black-capped vireo.

Gil Eckrich records a burst of photos of a black-capped vireo in the instant before it disappears. Now enjoying photography in retirement, Eckrich spent over 20 years as a biologist at Fort Hood. From his perspective, “31 years ago, black-capped vireos were scarce and difficult to find on the installation; these days… the species can be found in practically every training area.”

In 1988, one year after U.S. Fish and Wildlife Service listed the species as endangered, researchers scoured Fort Hood and found fewer than 200 of these migratory songbirds. In contrast, surveys in 2021 found over 8,500. Partly because of the dramatic increase of this population, U.S. Fish and Wildlife Service delisted the species in 2018. Control of brown-headed cowbirds and habitat management were the keys to the vireo’s recovery.

Cowbirds lay their eggs in the nests of other species relying on them to raise their young. However, when one chooses the black-capped vireo as a surrogate parent, the nest usually fails. The vireo eggs never hatch or nestlings die after the larger cowbird hatches.

It became clear in the late 1980s that cowbird removal was needed to boost vireo nest success when Fort Hood biologists found their eggs in over 90 percent of vireo nests. Using traps baited with live cowbirds, biologists ultimately reduced nest parasitism to less than 10 percent.

Fort Hood shares its cowbird trapping expertise widely and effectively extends its efforts beyond the installation boundaries by supplying over 20 other programs with cowbirds to stock their traps.

Wildlife biologist Scott Rowin at Balcones Canyonlands National Wildlife Refuge elaborates, “Because of these initial bait-birds we are able to trap approximately 1,000 cowbirds each year, many of which we later provide to dozens of central Texas landowners so they too can trap cowbirds. It all however starts with the initial birds we get from Fort Hood.”

Black-capped vireos nest in habitats with abundant shrubs interspersed with grassy areas. This structure promotes dense foliage at the edges of shrub patches because direct sunlight can reach the leaves. Vireos conceal their nests in this zone. In Central Texas, ideal habitat often develops 3-5 years after a fire or mechanical brush thinning. Fort Hood uses prescribed burns to enhance habitat for the vireo but also to reduce the chances that military training will spark unpredictable, damaging wildfires.

Furthermore, Virginia Sanders, Fort Hood endangered species program manager says, “the grasslands and shrublands that fire promotes, provide open space for military maneuver training.”

Fort Hood biologists conduct prescribed burns in partnership with the Balcones Canyon lands National Wildlife Refuge wild land fire crew. The combined team operates during the winter months and treated 18,783 acres in the last year. This cooperative effort benefits both partners.

According to Carl Schwope, fire management officer at Balcones, “[My] crew is able to increase their knowledge and experience base assisting Fort Hood with their management needs. This increases the crew’s capacity to achieve management objectives at Balcones.”

Habitat management and cowbird trapping gave the black-capped vireo a place to nest and the chance to successfully rear their young at Fort Hood. Although individual vireos may disappear into the shrubs, the continuation of these management practices promises to prevent their permanent disappearance.

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