Courtesy / Gil Eckrich, DPW-Natural and Cultural Resources volunteer
Citing the success of conservation measures that have boosted the population of the Central Texas songbird, federal officials announced that the black-capped vireo will be taken off the endangered species list.
At the time of its listing in 1987, the vireo’s numbers had declined to 350 known birds throughout its range in Texas, Oklahoma, and Mexico. The dwindling population was a result of people altering its shrubby habitat, grazing by livestock, and another bird species laying its eggs in vireo nests, U.S. Fish and Wildlife Service officials said.
Since then, vireo numbers have grown substantially, thanks to work by the states, the U.S. Army, Mexico, private landowners, and environmental groups, federal officials said in a news release Friday .
The vireo, which spends its winters along Mexico’s Pacific coast, now has a summer breeding range that includes the Mexican states of Coahuila, Nueva Leon, and Tamaulipas; five Oklahoma counties and 40 Texas counties, including Bexar County. Wildlife experts logged 5,244 male vireos in those locations from 2009 to 2014, according to Fish and Wildlife.
“The delisting of the black-capped vireo clearly illustrates the value of the Service’s partnership-driven approach to conservation,” said Amy Lueders, Fish and Wildlife’s southwest regional director, in a prepared statement.
A significant portion of the bird’s summer habitat lies on protected lands, with 40 percent of the vireo’s known population concentrated at Fort Hood near Killeen; Oklahoma’s Fort Sill and Wichita Mountains Wildlife Refuge; and Kerr Wildlife Management Area in Central Texas.
The insect-eating vireos rely on areas with “low scrubby growth” interrupted by open spaces and the occasional tree, according to Fish and Wildlife.
Much of the research to better understand vireos and the threats they face was done at Fort Hood, which is also home to what experts call “donut habitat.” That’s a central clump of tall brush surrounded by lower shrubs formed when tanks and other heavy vehicles drive off-road.
“I’m proud of our Natural Resources team for their application of sound science to demonstrate military training is compatible with the black-capped vireo recovery,” said Col. Henry Perry, commander of U.S. Army Garrison Fort Hood, in a statement. “I also appreciate the efforts of the U.S. Fish and Wildlife Service to fully understand our training and readiness requirements, striking a balance between Fort Hood’s mission and endangered species management.”
To ensure the vireo’s survival after losing its mantle of federal protections, Fish and Wildlife officials also announced a 12-year monitoring plan with help from the Texas Parks and Wildlife Department, Oklahoma Department of Wildlife Conservation, the Army, the Nature Conservancy, and Big Bend National Park.
Funding the plan, which is expected to cost $3.7 million, “presents a challenge for all partners”, Fish and Wildlife officials wrote, including caveats that make some nervous about the species’ survival.
“I do think we have seen a tremendous recovery of the population, and my main concern going forward is that we maintain this success and don’t forget how we got here,” said Chad Wilsey, director of conservation science for the National Audubon Society, who did his doctoral dissertation on vireos at Fort Hood.
If not properly managed, the vireos face a continued threat from cowbirds, which lay their eggs in other birds’ nests. Cowbird eggs often hatch first and their nestlings grow quickly, crowding out the nestlings of their host parents.
Studies done at Fort Hood show that more than 90 percent of vireo nests can end up being affected by cowbirds without ongoing trapping and other control techniques, according to Fish and Wildlife. An acceptable rate should be 40 percent or less, they state.
Vireos have also benefitted from a decline in sheep and goat raising throughout the Hill Country. The grazing livestock remove vegetation at the height the birds need.
Fish and Wildlife officials first announced their plan to remove endangered species protections for the vireo in 2016, a decision that stemmed from a petition by the Texas Farm Bureau and other groups to change the status of the vireo and four other Southwestern plants and animals.
Several groups responded to the proposal and the final rule with concerns about the vireo’s continued survival, including the City of Austin and Travis County, which manage preserve lands set aside to protect vireos.
In an April 11 letter, officials with the City of Austin’s Wildland Conservation Division called the monitoring plan “premature and based on subjective and unsupported criteria.”
Travis County Judge Sarah Eckhardt wrote in 2017 that the proposal “relies too heavily on assumptions that conservation efforts will continue throughout the bird’s range after delisting.”
In the San Antonio area, the bird has drawn less scrutiny than the region’s other endangered songbird, the golden-cheeked warbler. The vireo has much less potential habitat in Bexar County than the warbler, according to consultants working for Bexar County and the City of San Antonio.
Still, the vireo was included in an ongoing habitat conservation plan overseen by the City and County. Landowners and developers who participate in that plan can pay into a fund used to preserve bird habitat to offset any habitat loss caused by their projects.
No one has used the plan for the black-capped vireo, said Melissa Ramirez, assistant director of land development for the City of San Antonio.