Researchers study black-capped vireos

by John Starkey and Amanda Deats-Coello
photo by John Starkey photo by John Starkey

Ozona—The Escondido Draw Recreation Area is located less than 35 miles southwest of Ozona. The Escondido Draw is an area where small yellow and black songbirds with blackheads, red eyes, and white specks, known as black-capped vireos, make their warm-weather homes. These birds spend April through July in the Edwards Plateau and eastern Trans-Pecos regions of Texas.

These vireos were once on the endangered species list, but due to conservation efforts of the U.S. Department of Fish and Wildlife Service and a private environmental consulting firm, they are on a watch list. So, once a year, expert John Maresh comes to make sure they do not return to the list.

“Escondido Draw Recreation Area is a property owned by the Texas Motorized Trails Coalition, and they receive funding from the state and the federal highway administration to develop the park. Part of the agreement for accepting state and federal funds is to survey for and manage certain areas for black-capped vireos.

“They brought in a private environmental consulting firm to survey and census the black-capped vireos. We have been monitoring the vireo population here ever since. It’s been taken off the endangered species list, but there is a post-delisting monitoring period. That period varies by species and circumstances. The post-delisting monitoring period for the vireo is 12 years, and we are on the sixth year of that.”

The tiny black-capped vireos, about 4.5 inches long, are very fast flyers. They most often build cup-shaped nests in the fork of shin oak or sumac bushes and return to the same area to nest each year.

Maresh has been researching this species for 25 years. He studies how they are distributed around the state. He also researches the golden-cheeked warbler, which remains on the endangered list.

“There are sorts of variables to having an endangered species on land. For private property, the only thing is not to kill the individuals; you don’t have to protect the habit or anything,” he said.

More reporting is involved when the birds reside on public land and federal funds are involved.

“The government needs to know what is going on, how funds are being used, and how the funds will affect the species,” he said.

Maresh said it is also important to keep people away during the birds’ breeding season and watch for noise disturbances.

“Vireos are only here half the year or less. They migrate to southwest Mexico in the winter. So, trail building and clearing need to occur outside of breeding season so that you wouldn’t destroy a nest,” he said.

During this monitoring period, researchers are deciding whether the vireo population is stable, robust, and producing and whether the birds should be removed from the list.

He said the goal is to keep them off the endangered species list, detect problems, and address them early.

“We didn’t find a lot of nests here today. We saw two family groups: adults feeding their fledgling,” Maresh said.

The first year of survival is low, but the average life span is four to nine years. Some have been recorded living as long as 12 or 13 years, Maresh said.

The biggest issue vireos contend with is the brown-headed cowbird, he said. These birds lay eggs in the vireo’s nests and then eject the baby vireos.

“I’ve seen places where the reproduction is zero because every nest was hit by a cowbird,” he said.

“We have over 100 different bird species. There are roughly 3,900 acres in the park,” Tom Anderson, president of the Escondido Draw Recreational Park Board, said. He said he has seen very few people travel to the park to find the black-capped vireo, but the park will soon have cabins with electricity and AC, and maybe more bird watchers will come.

Currently, the Escondido Draw Recreational Park has campsites and 35 RV sites with full hooks up to electricity and water.

Ozona July