Every spring and summer, the expansive trees near the San Antonio Zoo at Brackenridge Park host dozens of egrets and yellow-crowned night herons that use the trees as nesting sites, known as rookeries.
Along with their beauty, the birds bring a host of problems, including droppings scattered all over walkways, the bodies of dead nestlings dangling from trees, and bacteria from the dead birds and their waste entering the San Antonio River.
But the birds have many supporters, some of whom were upset to see City crews trimming trees’ limbs and allegedly removing nests over the past few weeks.
Some of the bird lovers pointed to strict protections for nesting migratory birds, including egrets and night herons, under the Migratory Bird Treaty Act, which makes it unlawful to harass nesting migratory birds or do anything that would harm their eggs.
“It just kind of does something to me when you see them removing birds’ nests,” said Sarah Fitzsimons, who visited the park in late February and snapped photos of City workers in bucket trucks extended into the canopies of oak trees along the river.
Currently, the City’s goal is to maintain the trees at Brackenridge Park without harassing birds that have actually begun nesting, said Grant Ellis, natural resource manager with the City’s Parks and Recreation Department.
Ellis said the parks department consulted with Jessica Alderson, an urban biologist with the Texas Parks and Wildlife Department, who told them how to avoid pruning limbs that support nests with eggs in them.
“It’s a matter of tree management and making sure we don’t run afoul of existing laws and regulations while we are engaged with our tree management,” Ellis said.
In 2015, Alderson said City officials sought her help in getting the egrets and herons to move to different trees further downstream and away from people.
The droppings were an issue, she said, as were the carcasses of young birds hanging from their nests.
“It’s normal for them to have high mortality,” Alderson said. “That’s disturbing for people to see, but it’s normal.”
The egrets and herons are also “a significant source of E.coli [bacteria] in the park when they are nesting, along with the ducks and the geese,” said Rebecca Reeves, senior quality control and monitoring scientist with the San Antonio River Authority, in an email.
These birds naturally roost in larger rookeries over water, “and they will likely just choose another place to roost over water if they are discouraged from nesting in the park,” she said, adding that the River Authority is encouraging visitors to the waterway not to feed the birds to help reduce bacteria in the river.
In 2015, City crews tried trimming back tree canopies, hanging iridescent strips from branches and balloons with bulls-eye markings known as “bird scare eye balloons,” Alderson said.
It proved fairly effective, cutting down on the population of the nesting sites by about half, she said.
But over the next two years, City workers didn’t repeat the measures, and the birds returned, she said.
“It’s a constant thing that you’re going to have to keep doing,” she explained.
Ellis maintained that this year, at least, the City’s work was all about maintaining the trees, not about moving the birds.
“That was not really part of our intent this year,” Ellis said. “If there was going to be an effort to relocate, it would involve more than trimming trees.”
It does appear that some nests were removed during the tree-cutting. Three trees outside the Brackenridge Park Conservancy building showed signs of multiple pruned limbs. Around 10 night herons were perched in the branches, with a few rebuilding nests of twigs.
Alderson said it is okay to do this as long as the nests don’t have eggs in them.
“Once that egg is laid, everything pretty much has to stop,” she said.
With egg-laying about to begin and their tree maintenance work done, Ellis said City crews will not be returning to the rookery anytime soon to cut branches.
Alesia Garlock, a bird lover who regularly photographs and observes the egrets and herons at the park, said she wants everyone to know these birds are protected and has been trying to get the City to put up signs near the nests.
“We’ve just got to let the public know they’re here and not to be disturbed,” she said.