FORT HOOD, Texas - After months of planning, coordination and a lot of patience, the U.S. Fish and Wildlife Service and Directorate of Public Works' Natural Resources Branch here have successfully monitored and filmed a black-capped vireo nest.
On April 7, Sydney Dragon, a Student Conservation Association intern for the USFWS from the Arlington Ecological Services Field Office, came to Fort Hood and set up game cameras to monitor the secretive birds known as black-capped vireos. They gathered footage for three months, collecting more than 90 video clips.
“Using trail cameras can be an effective way to monitor secretive species,” Dragon said. “Many amazing moments were caught on camera.”
Black-capped vireos were added to the List of Endangered and Threatened Species by the U.S. Fish and Wildlife Service in 1987, when only 350 birds were known to exist. A tiny, four-inch bird, the black-capped vireo is usually heard long before it is seen. The songbird sings loud, distinct songs, which help biologists locate the nests, which are built two to four feet off the ground, usually in thick foliage.
The camera was set to record for 30 seconds when movement was detected. Scott Summers, environmental protection specialist with the Directorate of Public Works’ Natural Resources Branch, was in charge of checking on the camera every few days, replacing SD cards and seeing if the nest had populated.
“We were surprised to see the Carolina wren visit the nest, and we were jumping for joy when we found the footage of the painted bunting visiting the nest with food in her mouth,” Dragon explained. “We got to see the diversity of insects the black-capped vireo parents brought the chicks, and witness the insurmountable care these parents provided for their nestlings.”
The unusually rainy Central Texas spring and summer caused some issues. Summers feared continued rain might lead to fewer chances to capture high-quality images due to lens moisture and less bird activity, among other problems.
Summers was cautious when approaching the cameras, so as not to disrupt the birds’ natural behavior. Their hard work paid off, receiving better footage than they ever hoped.
“The clips of the black-capped vireo family at the nest is my favorite,” Dragon said after seeing the footage. “Seeing both parents tend to the nestlings together is truly a precious moment.”
Dragon said black-capped vireo parents share nesting duties, such as incubation, feeding and brooding. After the nest is built, one egg is laid per day, until the usual full clutch of four eggs are in the nest. The eggs are then incubated for 14-19 days. As newborns, the chicks are naked, blind and completely dependent on their parents, who both feed their young. They open their eyes around day five after birth, have most of their feathers by day 10 and normally fly the nest around day 12.
Summers said they ended up filming four different nests, but only two of them provided optimal pictures and footage. After seeing the first hatchling, Summers said he really hoped it would live to adulthood for a couple of reasons: he dislikes seeing nests fail after he forms an emotional attachment, and he was hoping to finalize the footage sooner than later, given all the recurring rain.
“Unlike hawks, who can defend nests better by being a counter-threat to danger, songbird nests are more susceptible. It is tougher being a songbird,” he explained. “But fortunately, songbirds have a better-than-average chance here at the Great Place.”
Summers said that Fort Hood and the Army are good stewards of their land, which results in better habitat and the chance for wild songbirds to thrive. He said a premium habitat made it easier to take enough quality footage in a short time, despite the rains.
One of the biggest threats to the black-capped vireo population are brown-headed cowbirds, a parasitic species of bird that, if left uncontrolled, are detrimental to vireo nests. Summers said brown-headed cowbirds are considered obligate brood parasites because they do not nest or care for their young. Instead, the cowbirds lay their large eggs inside other bird nests. The larger cowbird nestlings then outcompete the vireo chicks for food, which historically reduced the black-capped vireo population.
Summers said 2013 Fort Hood Garrison Hall of Fame winner John Cornelius, a biologist who studied the birds here in the mid-1980s, discovered 90% of the nests were parasitized by cowbirds. In 1989, Fort Hood estimated there were less than 200 male black-capped vireos on the installation. After partnering with the U.S. Fish and Wildlife Service to save the species, Fort Hood’s Natural Resources Branch decided they needed to control the population of cowbirds to help recover the black-capped vireos.
The birds were removed from the endangered species list in 2018 thanks to a resurgence in the population. In 2019, there were an estimated 8,000 male black-capped vireos located at Fort Hood, a sustained and steady increase over the last 30 years.