The tiny island in the middle of Elmendorf Lake that was once knotted with gnarled trees, dead vegetation and more than 1,000 birds now looks clean and open. Only a few bare trees remain. Neatly raked soil covers the ground. A scant number of birds perch at the island’s edge near Our Lady of the Lake University.
Bird Island, a quarter-acre dot of land, is unrecognizable.
The U.S. Department of Agriculture and the city of San Antonio’s Parks and Recreation Department have teamed up in recent weeks to divert large masses of cattle egrets from the island with hopes of stopping them from flying over Joint Base San Antonio-Lackland and Port San Antonio. The exercise aims to minimize the risk of bird strikes with airplanes.
City workers and contractors changed the island’s landscape by removing dead materials and old nests last month. They pruned the remaining live vegetation, cutting 50 to 70 percent of the trees’ canopy to make the spot less enticing to cattle egrets. They also dispersed two types of seed to encourage new growth.
USDA employees began conducting daily diversion or “harassment” exercises in mid-December, using startling noises and visuals to keep the birds from returning. That campaign will continue every evening through March.
For two hours every night, workers slam clapper boards together and shine lasers or handheld strobe lights. Sometimes they fire up inflatable figures staked to the ground, which act as scarecrows of sorts. Other times they fire pyrotechnics into the air — like fireworks without the colorful patterns.
The diversion exercises must persist beyond mid-February, when the nesting season for cattle egrets begins.
“Once they get to that point where they have to build a nest and lay an egg and they’re realizing they’re not going to be allowed to do it at that location ... they will give up and go somewhere else,” said Cory Wilson, a wildlife biologist with the USDA’s Animal and Plant Health Inspection Service.
On ExpressNews.com: San Antonio begins clearing out Bird Island
Ideally, USDA workers hope the cattle egrets move to Mitchell Lake Audubon Center 11 miles away.
Wilson refers to the noisy harassment campaign as “conditioning” exercises.
“This was a project based on risk management and hazard management — it wasn’t necessarily a nuisance issue,” he said. “There’s no cause to be mad at these birds because they exist. It’s because there’s a true threat to health and human safety for the aircrews at this point.”
The Federal Aviation Administration traditionally requires airports to identify any wildlife hazards within a 5-mile perimeter of its runways, Wilson said.
In recent years, 500 to 700 cattle egrets have nested at Bird Island throughout the winter. In the spring, up to 1,000 to 1,200 stop there as the migratory population arrives.
Because of that large volume of bird traffic, the island became unsightly.
“The number and the concentration of birds that existed on that island were actually causing a collapse of the vegetation,” Wilson said. “Most of the vegetation that was removed was actually dead just from the buildup of the fecal material on the ground.
“When they establish these rookeries ... they’ll literally kill the trees in that area and then just kind of move on. That is a sometimes a byproduct of that colonial nesting bird behavior.”
On ExpressNews.com: Cattle egrets on San Antonio’s Bird island to face shock and awe
The accumulation of bird droppings changed the balance of Bird Island’s soil. Some trees grew sideways because of the sheer number of birds nesting in them. Most of those trees died and have been removed, said Bill Pennell, the city’s assistant manager of park planning.
Bird Island is at the western end of Elmendorf Lake Park, which the city spent $15 million revitalizing in recent years. The island — accessible only by kayak or canoe — serves as “a critical nesting site” for the snowy egret, great egret, neotropic cormorant, double-crested cormorant and great blue heron, according to signs at the lake.
The city spent $32,000 cleaning up the island, Pennell said.
Such projects are infrequent for the USDA.
“We might physically do one of these projects every five years,” Wilson said. “But we do offer a lot of technical guidance to allow different municipalities or other agencies to do the same things that we’re doing here.”
Such jobs are becoming more common for cities and parks as development continues, Pennell said.
“Birds and other animals still need areas to go. With reduced areas and spaces for wildlife, they’re going to find places. ... So it will put stress on any habitat that can’t handle that,” he said.
Peggy O’Hare reports on the census, demographics and occasionally crime and general assignments in the San Antonio and Bexar County area. Read her on our free site, mySA.com, and on our subscriber site, ExpressNews.com. | pohare@express-news.net | Twitter: @Peggy_OHare
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