Peregrine falcons find a home in Chicago

(Published April 29, 2019)

Abhinanda Datta, Staff Writer

If you spot a mid-sized raptor swoop in at incredible speed and catch another bird in flight, don’t be surprised—it is just a peregrine falcon.

Found throughout the world, these birds have found a home in the Midwest, with more than 20 American peregrine falcons in the Chicagoland area.

With a body length of 15 – 20 inches, the peregrines can attain a speed of 200 mph when diving on their prey.

According to Mary Hennen, collections assistant in the Bird Division at the Field Museum, an estimated 400-500 pairs of Peregrines once nested in the Midwest and eastern United States. But by the 1960s, the species had been wiped out regionally.

“The primary cause was the buildup of DDT and its byproducts in the birds,” she said. “These accumulated chemicals caused abnormal reproductive behavior in adults and thinning of shells, which led to egg breakage.”

The Chicago Peregrine Program began in 1985 as a cooperative effort between the Chicago Academy of Sciences, Lincoln Park Zoo, Illinois Department of Conservation and the Illinois Audubon Society, with the aim of restoring the population.

From a single breeding pair at a Chicago-Wacker site in 1988, Illinois had 12 breeding pairs in over 23 different territories by 2011.

“Although Peregrines still remain endangered in some states, in Illinois, the population has rebounded. In fact, our Peregrine status has been upgraded from endangered to threatened,” Hennen said.

In May, eggs that were laid during March-April, are incubated for about 30-32 days. The male and the female take turns looking after the eggs. Hatching begins in mid-May or around Mother’s Day.

“This is also the time period where the adults are most defensive of the nest site. Males will spend most of their time hunting in order to feed the female and chicks,” Hennen said.

In the coming months, especially around mid-June to July, people can see the peregrine fledglings’ first flight as they glide down from the nest site. People can also observe the birds through the Illinois Peregrine Webcams found on the Field Museum website. For more information, visit fieldmuseum.com.

A peregrine falcon from a 2018 webcam in Rockford. Photo courtesy the Field Museum

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