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Editor’s Note: This writer is a member of the Texas Hill Country Heritage Association.
Anyone who’s been to an agriculture extensional range or wildlife management program would have recognized the format of the Biodiversity Works’ Golden-cheeked Warbler and Black-capped Vireo Symposium held on Jan. 28-29 in Austin: six or seven speakers a day, crowds around the coffee urn, catered lunches, old pros chatting in the back, and the inevitable PowerPoint presentations. This year, however, there were differences.
The Symposium was held at the Lady Bird Johnson Wildflower Center auditorium in Austin, a beautiful example of Southwestern architecture. It was a bit of a change from the various livestock show barns and working ranch equipment sheds at most AgriLife programs.
Breakfast tacos for the morning break and a vegan option for the catered lunches were pure Austin touches. Last but not least, the crowd was made up of supporters of the Endangered Species Act, people who actually care about the survival of endangered songbirds.
The first speakers of the morning focused exclusively on the Golden-cheeked Warbler and its preferred habitat – mature Ashe juniper forests. Representatives from the U.S. Geological Survey and Texas Parks & Wildlife discussed habitat conservation and Golden-cheeked Warbler population trends on the Balcones Canyonlands National Wildlife Refuge and other protected sites. James Mueller, with the U.S. Fish and Wildlife Service, exhibited data on managing juniper-oak woodlands with an emphasis on density of cover.
After a break, representatives of Pronatura Sur, a Mexican conservation group, presented statistics of the Golden-cheeked Warbler’s winter range in Mexico and Central America. Claudia Macias-Caballero showed what warbler conservationists in Texas sometimes forget: most warblers and vireos spend more time in the tropics than in the U.S. and their behavior there is rather different than here.
Great flocks of warblers and vireos of different species fly and feed together through the mixed upland pine-oak forests of Central America. The greatest threat there to the birds is deforestation, Macias-Caballero added, as economic development brings commercial logging in addition to local people’s gathering of firewood and charcoal burning.
The afternoon started with Ashley Long who reported observations from her research for the Texas Department of Transportation about how road and construction noise affects nesting songbirds in Real and Uvalde counties. Surprisingly, the research had found that the adverse effects increased at slightly greater distances from the roadways.
William Reiner presented a fascinating study of the physical territories of nesting Golden-cheeked Warbler pairs on the Balcones Canyonlands Preserve near Austin. In a very thorough multi-year project they discovered that the territories of nesting pairs can significantly overlap. They also discovered that adult Golden-cheeked Warbler will occasionally feed the young of other pairs.
This led to some discussion about the evolutionary advantage of this behavior, raising the question, “Can the overlap of territories affect census survey data?” A good question, given the claims of a recent delisting petition filed by some former and current Texas state officials.
Protecting the Golden-cheeked Warbler in Fort Hood has also been questioned recently by supporters of delisting the bird from endangered species status. Rebecca Peak has studied warbler’s nesting survival in different habitats there. She found that smaller cedar brakes and areas cut up by roads had lower nesting success.
She credited Fort Hood’s aggressive control of the Brown-headed Cowbird with cutting down nest predation and nest parasitism by this pest. They discovered that rat snakes, great climbers with a taste for eggs, are a greater threat to Golden-cheeked Warbler nesting success than cowbirds there.
The day ended with a short overview of the Bandera Corridor Conservation Bank, a commercial program that sells Endangered Species Act mitigation credits for developers and benefits conservation-minded ranchers. A wine and canapé social followed.
Friday morning began with the heavy hitters: the U.S. Fish and Wildlife Service. Omar Bocanegra and Chris Harper started with the inevitable PowerPoint showing how the Fish and Wildlife Service lists and delists species under the Endangered Species Act and how they handle petitions for listing or delisting candidate species.
There are current petitions before the Fish and Wildlife Service to delist both the Golden-cheeked Warbler and the Black-capped Vireo, but because these petitions are currently under consideration, the service representatives were unable to comment much on these matters.
Fort Hood has a long history of Golden-cheeked Warbler recovery efforts and some of the best planning to coordinate cattle grazing and songbird habitat management. David Cimprich of Fort Hood’s Natural Resources Management Branch discussed post-breeding movements of Black-capped Vireo on the military installation. This was a rather technical report on population movements that could have bearing on future census work.
Scott Summers, another Fort Hood employee, outlined control techniques for the Brown-headed Cowbird. Summers seems to have really mastered cowbird trapping. He recommended placing the traps in open fields where cattle graze, using plenty of live decoy birds to lure cowbirds into the traps, and placing them near a tree or snag that the birds can light on before entering it. He also reported and recommended just shooting the pests, himself using a 20 gauge shotgun with fine steel shot.
Jennifer Reidy, who had addressed urbanization of songbird habitats earlier that morning, presented findings of an experimental comparison of Golden-cheeked Warbler habitats recovering from prescribed burns to undisturbed habitats. Butch Taylor’s work notwithstanding, burned juniper forests supported fewer Golden-cheeked Warbler nesting pairs than directly adjacent unburned juniper.
The U. S. Fish and Wildlife Service’s Balcones Canyonlands National Wildlife Refuge is intended to provide protected habitats not just for the Golden-cheeked Warbler, but for the Black-capped Vireo as well. Biologists noted that as shin oak brush cover on the refuge gets thicker it becomes less attractive to Black-capped Vireo.
A large pasture that had once supported fair numbers of vireos was described by Dr. Dale Rollins as “brush sculpted,” the process of cutting and clearing land to increase wildlife populations. James Mueller of the U.S. Fish and Wildlife Service reported that Black-capped Vireo populations fell drastically after the clearing, not returning to optimal numbers until four years later.
The only research reported at the symposium that was not sponsored by government or academia was Jennifer Blair’s “Black-capped Vireo Results of a Reconnaissance Survey in Mason and Menard Counties.” Blair, a certified wildlife biologist at Bowman Consulting Group, was asked by Braun & Gresham, a law firm, to complete a fence-line survey along the boundaries of a proposed wind turbine development in northwestern Mason County and an adjacent part of Menard County.
The survey was paid for by the Texas Hill Country Heritage Association, a private property rights and wildlife and rangeland conservation organization based in Mason County. In 2015, over the short span of four days, Blair’s team discovered over one hundred Black-capped Vireo and one Golden-cheeked Warbler along the fence lines and public roads adjacent to properties leased by Enel Green Power North America’s 10,000 acre Mason Mountain Wind Project.
The last regular presentation of the day was Lisa O’Donnell’s “Historical Ecology of the Texas Hill Country.” O’Donnell, a City of Austin employee, used historical records to demonstrate that juniper forests and thickets had been much more prevalent in Central Texas before European settlement than is popularly believed.
Using only first-person sources from the earliest written accounts of settlers’ experiences along the Balcones Fault region, O’Donnell expressed skepticism of the conventional wisdom that extensive cedar thickets are an artifact of historical Anglo-Texan ranching. Her thesis, preservation of cedar thickets being part of land management for the Golden-cheeked Warbler, led to the last event of the day, a panel discussion: “Can We Improve the Public’s Opinion of Ashe Junipers to Facilitate Conservation and Recovery of the Golden-cheeked Warbler?”
There were no ranch or other agricultural interests represented on the panel and it was hard to see how the landowners who control most Golden-cheeked Warbler and Black-capped Vireo nesting habitats could be reached through the Biodiversity Works discussions. Still, the panelists admitted they have a hard job ahead of themselves.