A Chicago museum disrupted an endangered bird's habitat

Renovations to the Chicago History Museum in 2021 drove black-crowned night herons away from their annual breeding grounds. The birds have not returned, conservationists say.

Black-crowned night herons (pictured, a bird in Florida's Audubon Corkscrew Swamp Sanctuary) are endangered in Illinois. 
Photograph by Fritz Polking, VWPics/AP

Since 1856, the Chicago Historical Society has carefully preserved artifacts and documents that catalog the heritage of the Windy City. Its collections are housed in the Chicago History Museum, a structure erected in 1932 in the city’s Lincoln Park neighborhood several blocks from Lake Michigan. The building has been expanded multiple times and now boasts an array of sleekly curated exhibits.

In 2021, the museum broke ground on an effort to modernize its shaded lawns. The project included the construction of a walking trail with signs highlighting Chicago history, the installation of native plantings, and the reinforcement of the ceiling above its leaky underground archives. The work was designed, in part, to make the space a more attractive venue for high-dollar events like weddings and fundraisers.

The area, however, was also adjacent to a long-standing breeding ground for at least 45 pairs of black-crowned night herons, which are listed as endangered in the state of Illinois. Museum officials were not only aware of the herons, staff and visitors even enjoyed having an endangered bird’s rookery on the museum’s grounds.

“The birds had been around for a while,” John Russick, senior vice president of the museum, told National Geographic. “It was kind of cool that they were here.”

Yet museum officials appeared to minimize possible damage to the birds’ rookery that a major construction project would cause. Based on the museum’s limited assessment of the birds, the Illinois Department of Natural Resources conducted a brief environmental review and found the renovation posed little risk of disruption to the herons. Teams of workers arrived in March of 2021, just before the herons’ annual springtime nesting season. The crews operated loud equipment at times only a few yards from the rookery.

Soon after, the birds abandoned their nests. Weeks later, crows were seen scavenging on dead nestlings. In 2022, a handful of male herons returned to the site, but after failing to attract mates, they left.

The museum maintains that it followed all appropriate steps to limit the impact of the construction on the birds.

“We tried to mitigate as much of the heavy work as we could during that time period,” says Russick.

But environmental and wildlife advocates think more could have been done to prevent harmful impacts on the birds. Amy Lardner, a conservationist who in 2022 founded the Chicago Black-Crowned Night Heron Project, had obtained permission from the museum to monitor their progress. She visited the site shortly after construction began and said she found the scene disturbing. While some trees had been partitioned by fencing, the rest of the property was bare dirt. The construction noise went from early morning to late afternoon.

“I initially thought, ‘Well, it's a quiet time at the rookery,’” Lardner says. “But as time passed, I was seeing fewer and fewer adults and hearing no chicks. I knew by the middle of May that things were not on track.”

Herons under encroachment

The museum project is not the first time black-crowned herons have experienced reductions of crucial habitat in Illinois. While the birds can be found on every continent except Australia and Antarctica, and are populous in parts of the U.S., they have been listed as endangered in Illinois since 1977. 

Surveys in the 1980s and 1990s reported as many as 70 breeding sites. Today, the only major breeding colony in the state is in Chicago’s Lincoln Park Zoo. Small colonies persist along the Fox River and another large colony remains at an industrial site in nearby Indiana.

In the past three decades, human development of freshwater habitats, which the herons need to survive, has been the main driver of habitat destruction. But the herons face threats from non-human competitors as well. Colonies in the Chicago suburbs at Lake Renwick and Baker’s Lake were eventually overtaken by aggressive double-crested cormorants.

Walter Marcisz, the former president of the Chicago Ornithological Society, remembers seeing massive numbers of herons emerging from the colonies surrounding Lake Calumet on Chicago’s Southside, one of the species’ last redoubts.

“The highest number we got in a single day flying out of the colonies was around 1,500,” he recalls.

Beginning in 2002, Marcisz helped Jeffrey Levengood, a University of Illinois wildlife toxicologist, track the herons’ nightly expeditions to feed on invasive alewives—a type of fish—in Lincoln Park on Chicago’s Northside. A series of floods and droughts later drove the herons north permanently, where they began nesting in the dense canopies edging the neighborhood.    

Greg Neise, who at the time served as the staff photographer for the Lincoln Park Zoo, first noticed empty black-crowned night heron nests on an overgrown island located in South Pond adjacent to Lincoln Park Zoo in the winter of 2006. The following July, he photographed active nests.

However, in the winter of 2009, the trees that populated the island were cleared as part of a restoration effort. Though mature trees were planted as replacements, the herons did not return to breed the following season.

They relocated to an allée of trees in the neighboring parklands to the west and small numbers began nesting above the Children’s Zoo in Lincoln Park Zoo. By 2010, all the herons had vacated the Calumet area and settled into Lincoln Park.

Then, in 2014, they again came into conflict with local interests. The removal of the trees due to damage by emerald ash borers and the herons’ guano pushed the birds toward the zoo and other areas of the park. By 2015, they had set up camp on the grounds of the Chicago History Museum.

A shortened environmental review

Around the same time, the history museum was accelerating plans for a redevelopment of its site, which sits on land owned by the Chicago Park District.

In April of 2020, the museum, via its primary contractor, filed a request for an EcoCat consultation with the Illinois Department of Natural Resources, as required by state law. All state and local projects are subject to such an impact review in Illinois, a process that also occurs in other states and at the federal level through the National Environmental Policy Act.

The request for review mentioned both black-crowned night herons and the state-threatened longnose sucker, a fish inhabiting nearby Lake Michigan.

But it did not mention explicitly that black-crowned night herons were known to breed on museum grounds. It simply noted that herons were in the vicinity—a reference that could have been interpreted to mean the nearby colony at the zoo.

“At that time, we had no records of black-crowned night heron[s] at the museum, and the applicant made no indication that herons are known to nest on the museum grounds, so we terminated the consultation without recommendations,” said Jayette Bolinski, director of communications for the Illinois Department of Natural Resources, in an emailed statement. As a result, IDNR investigators never visited the site, and the review was closed a day later.

The Park District, which owns the land the history museum stands on but was not involved in the environmental review, suggested the onus was on the museum to flag the presence of sensitive wildlife conditions.

“Any and all construction in or around a Chicago Park District natural area or a known bird habitat is avoided during migration and nesting season,” said Irene Tostado, Park District deputy director of communications, in an emailed statement. She added that “the Chicago History Museum was responsible for management of the construction project, which included monitoring and documenting the presence of wildlife in the area as well as seeking approval for the project from IDNR.”

In the aftermath, Lardner, the conservationist, asked the IDNR to investigate the matter. The agency opened an investigation into whether there was an illegal “take” at the rookery on the museum grounds, an action that would potentially violate Illinois’ endangered species law. But officials eventually closed the investigation, citing the limited availability of information. The IDNR concluded that any potential offense did not rise to the level of a criminal matter.         

Seeking common ground

It is often difficult to balance the needs of human development with those of wildlife, especially in urban environments. In 2012, a colony of grey-headed flying foxes, a species listed as vulnerable by the IUCN and by Australian authorities, was pushed out of the Royal Botanic Gardens in Sydney, Australia because it was destroying much-beloved trees. In 2019, volleyball courts in Chicago had to be shut down and a concert canceled to accommodate a pair of nesting piping plovers. The species is listed as endangered in Illinois and on a federal level in the Great Lakes region.

This constant tension often pits conservationists against land-use experts and provokes debates about what it means to protect land for maximum use and enjoyment—and whose use and enjoyment should be prioritized.

Around the Chicago History Museum, the effects of the construction on the herons appear to be permanent. The herons have not returned to breed, and other than the straggly remains of several nests, there are few signs the herons were ever there.    

The evicted birds are believed to have retreated to the colony at the Lincoln Park Zoo, where they concentrate around a habitat devoted to the red wolf, a federally endangered canid. The zoo’s Urban Wildlife Institute reported a record 750 adult herons and 400 fledglings this year.

Except for a few small, isolated colonies, the rookery at the zoo appears to be the species’ last remaining breeding ground in the state.

Advocates hope that restoration efforts in the Calumet region aimed at creating habitat for marsh birds and other wildlife may help to draw some of the population south again to their historic breeding grounds.

Until then, the species finds itself restricted to its space at the zoo, surrounded by wolves and speeding cars, and reliant on the consideration of humans who now dominate what was once undisturbed wetland.

The National Geographic Society supports Wildlife Watch, our investigative reporting project focused on wildlife crime and exploitation. Read more Wildlife Watch stories here, and send tips, feedback, and story ideas to NGP.WildlifeWatch@natgeo.com. Learn about the National Geographic Society’s nonprofit mission at natgeo.com/impact.

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