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As black-capped vireo rebounds, people asked to monitor bird at Inks Lake State Park

Black-capped vireo

The U.S. Fish and Wildlife Service and Texas Parks and Wildlife Department are asking citizen-scientists to help monitor the black-capped vireo at Inks Lake State Park and report sightings or songs of the bird through the eBird app. iStock image

In April 2018, the federal government took the black-capped vireo off of the Endangered Species List, but the U.S Fish and Wildlife Service and the Texas Parks and Wildlife Department are still looking out for the bird, which can be found in Central Texas.

The service and department launched a citizen-scientist program to monitor the bird at Inks Lake State Park in Burnet County from April 10-July 1, which is its breeding period. Officials are asking people, particularly experienced birders, to report any sightings or songs of the vireo at the park via the eBird app, which is available in the Apple Store and on Google Play. 

“Under the Endangered Species Act, which is the law, when a species comes off it, (the act) requires that we monitor it for no less than five years,” said Omar Bocanegra, a supervisory fish and wildlife biologist overseeing the monitoring of the black-capped vireo for the federal service. “We actually extended it for 12 years for the black-capped vireo.”

The service, partner agencies, and private landowners continue to monitor the recovery of the black-capped vireo across its ranges in Texas and Oklahoma. Much of that effort takes place on what Bocanegra describes as Tier 1 properties, where a known population of 30 or more pairs of the black-capped vireo live. This includes the U.S. Army’s Fort Hood in Killeen. The 214,000-acre post plays an instrumental role in the species’ recovery with about 5,000 pairs of black-capped vireos. 

A Tier II property, Bocanegra said, is an area with fewer than 30 pairs of the bird.

Officials are not sure if black-capped vireos live in Inks Lake State Park, hence the citizen-scientist program. 

A lack of funding and personnel make it difficult to monitor Tier II properties, so the public has been called upon to help.

“Because resources are tight and (the vireo’s range is) a big area, we thought about citizen-scientists helping in places like Inks Lake State Park,” Bocanegra said. “This is first time we’ve done it with the black-capped vireo, so it’s a pilot program, but let’s see if we can detect any black-capped vireos at the park during the breeding period.”

People are asked to report any observations, including songs, of the black-capped vireo at the state park through the eBird app. When posting an observation comment, add “BCVI PDM,” which stands for “black-capped vireo post-delisting monitoring.”

“We can go in and pull all that data and information and see what we have,” Bocanegra said.

When monitoring:

  • surveys should occur between sunrise and 1 p.m.;
  • surveys must be conducted in clear weather — no fog, rain, or wind speeds over 12 mph;
  • learn the black-capped vireo’s call — you might hear more than one responding to each other;
  • count individual birds by separating your detection by 300 meters (as the crow flies);
  • don’t use audio playback of bird calls;
  • and always follow state park rules.

The eBird website has photos and recordings of the vireo for reference.

Population returning

The black-capped vireo is considered a major success of the Endangered Species Act. When it was added to the list in 1987, only 350 known pairs existed across its habitat. In 2018, when it was removed, the population was about 14,000 pairs.

The bird winters in southwest Mexico, but its breeding area includes a wide swath of Texas and parts of Oklahoma. When it nests, the black-capped vireo prefers to build about “doorknob” height with brush and other cover extending down toward the ground to hide it from other animals. 

Bocanegra said the black-capped vireo faced a couple of major threats that led to its low numbers in the 1980s. It preferred areas of Texas also favored by goats, which eat just about anything from doorknob height and down, leaving vireo nesting areas exposed, Bocanegra explained.

“Black-capped vireo won’t tolerate that,” he said. 

Another threat was the brown-headed cowbird, which doesn’t build nests of its own but instead seeks out those of other birds. Cowbirds take over nests to lay their own eggs, sometimes removing the first inhabitant’s eggs. 

Habitat loss also added to the black-capped vireo’s low numbers.

In response to these threats, the U.S. Fish and Wildlife Service teamed up with partners across Texas and Oklahoma, including state wildlife departments, the Nature Conservancy, Fort Hood, Fort Sill in Oklahoma, and private landowners, to trap cowbirds — something at which Fort Hood excels — and, in 1993, the federal government repealed the National Wool Act, ending some incentives for raising goats and sheep. This led to fewer goats grazing across black-capped vireo habitat.

Land managers also have resumed using fire to regenerate habitat, which aided the species’ return.

Even as the black-capped vireo population rebounds, protection efforts continue. 

“Just because it was removed from the (Endangered Species List) doesn’t mean we’re not monitoring it,” Bocanegra said. “This is the third year — third breeding season — since the delisting, and we’re seeing some good things. We’ve found some new populations. There’s a lot of encouraging news. Right now, we’re pretty impressed with the numbers we’re getting.”