The Chicago Peregrine Program announced Wednesday that four peregrine falcon chicks who lived on a University of Illinois Chicago building suddenly died. The organization could not confirm the cause of death, but one possibility could be bird flu.
“Today, be assured we are as sad as are all the UIC peregrine fans over losing 4 beautiful chicks,” the Chicago Peregrine Program wrote in a May 29 Facebook post.
The falcon chicks were sent to the Field Museum for evaluation of the cause of death.
Mary Hennen, the director of the Chicago Peregrine Program and assistant collections manager for the museum’s bird division, said the deaths were unusual because the chicks were more than 3 weeks old.
“Typically, though, when you lose a chick, it’s right after hatching, where they’re so vulnerable to weather because they’re tiny and they’re not able to thermo-regulate. But when chicks are older, stronger, healthier deaths are unusual,” Hennen said.
Hennen said one possibility for the cause of death could be from contaminated prey. A peregrine falcon’s main source of food is pigeons which could have gotten bird flu or consumed poisoned feed. She said the cause could be due to a physical issue with the chicks themselves.
Scientists at the Field Museum have not tested the birds yet, but Hennen said it could take until the fieldwork season is over.
The Midwest and Eastern U.S. were once home to peregrines, the fastest bird in the world, but in the 1960s, the raptors were nearly wiped out due to the accumulation of insecticides like DDT poisoning their food supply and damaging their reproductive health.
After the federal government banned DDT the Chicago Peregrine Program reintroduced the bird to several areas, and the population has rebounded. Currently, there are about 20 breeding pairs in the Chicago area.
Their numbers began dropping again, especially in coastal areas, with the bird flu outbreak. But city falcon that eat songbirds and pigeons among other birds, haven’t seen the same declines, experts say.
The Chicago Peregrine Program has now shut off the webcam used to monitor the chicks.
The four chicks were nesting on a ledge on the 28th floor of UIC’s University Hall. The parent birds are longtime UIC peregrine residents Mouse and Loop. They have made their nest at the school for more than a decade now, and peregrine falcons have been nesting at the school since 1999.
“While the loss of the chicks is difficult to accept, we are encouraged that our adult peregrines, Mouse and Loop, are doing well. We look forward to the 2026 peregrine nesting season,” UIC Department of Communication said in a news release.
Contributing: Associated Press