Several dozen mature trees in Lincoln Park revered by some as the seasonal nesting site of a species of heron will be cut down during the next two years because of disease and other problems, Chicago Park District officials said Wednesday.
Bird experts were delighted and surprised when the normally people-averse black-crowned night heron chose Lincoln Park as its main breeding ground in the state, but the species rarely seen in Illinois is facing a challenge from its urban environment.
A total of 57 mature trees in Lincoln Park, most of which have been the spring and summer nesting site for the stocky, black-backed, yellow-legged herons, will be cut down along a walkway at the south end of the park, Park District officials said at a Lincoln Park Advisory Council meeting Wednesday night.
About half of the “severely diseased and condemned trees” near the park's Benjamin Franklin monument will be cut down this winter and the rest next year, said Jason Steger, natural areas manager for the Chicago Park District's Department of Natural Resources.
Replacements for the trees cut down as well as others that have died will be planted in the fall, Steger said.
The zoo has monitored the herons since they showed up at the park about 2008. Lincoln Park Zoo's Urban Wildlife Institute last summer counted 250 nesting pairs, about 500 birds, in Lincoln Park, said Mason Fidino, the institute's coordinator of wildlife management. Forty percent of the birds nest in the walkway where the trees will be cut down, Fidino said.
Most of the 57 trees have nests on them, with up to 12 nests each, with one to seven eggs inside each nest.
“It is a sad thing that is going to happen, and this really shows how difficult it is to manage areas for both wildlife and people,” Fidino said.
To some birders, the plan is not just sad but a shock. These birds are easy to see in Chicago because of their choice of Lincoln Park, but they are rare to see outside the Chicago area, said Steve Bailey, an ornithologist at the Illinois Natural History Survey.
Historically, he said, they have been endangered from a loss of their nesting and foraging habitat.
“That is a shock to me. I can hardly believe they're doing it,” Bailey said.
“Most of the nesting black-crown night herons in the state are in Chicago, and most of them are in that (Lincoln Park) nesting colony, and to think they're going to cut down any of those trees is kind of mind-boggling.”
Fidino, who has been consulting with the Park District on its decision, said the trees are unsafe for herons. One tree fell over, killing most of the birds that were nesting on it, he said.
Most of the targeted trees are about 40 years old, Steger said, and many are lindens, Park District officials said. They will be cut down because they were poorly planted and managed, officials said. About half of the trees are ash, which have been infected by the invasive, deadly emerald ash borer, Steger said.
“A lot are just structurally compromised,” he said. “You can see that there are cracks in the center of them.”
The Park District has consulted with the zoo, the Illinois Department of Natural Resources and the U.S. Fish and Wildlife Service to remove the trees with as little disruption to the herons as possible, Steger said.
While Bailey feared that if the birds left, they would never come back, Fidino said the birds have proved that they are adaptive. Birds naturally shift colonies over time because they slowly degrade trees with their feces.
“While this removal is more abrupt than a slow decay, there are nesting opportunities in the park,” Fidino said.
Fidino said he believes the birds chose Lincoln Park because there is enough food in the Chicago River and beaches as well as creeks and smaller wetlands.
The presence of humans, he added, has limited the presence of predators.
“It's been kind of a joy,” Fidino said.
“They pretty much show up on April 1st.”
The herons this spring will either join a colony on other trees in Lincoln Park or start a new colony in other areas of the park and elsewhere.
“Which can be a risky maneuver,” Fidino said. “Because one night heron setting a nest in a tree doesn't mean another night heron would nest there.”
He believes that if they have adapted to the urban environment, they show promise to adapting to the reduction in trees.
“That's why we'll continue monitoring this species,” Fidino said, “just to see how this management strategy plays out.”
Tribune reporter Steve Johnson contributed.Copyright © 2015, RedEye