New Book Tracks Peregrine Falcon’s Return From Near-Extinction

The peregrine falcon’s diving speed of more than 200 miles an hour makes it the fastest member of the animal kingdom.

But by the 1950s, widespread pesticide use had wiped out the bird of prey’s population in Illinois, and it was nearing extinction in North America.

The new book “The Peregrine Returns” tells the story of the raptor’s recovery, featuring illustrations by Field Museum artist-in-residence Peggy Macnamara.

“If you count the Midwest and eastern part of the U.S., there were roughly 300-350 nesting pairs pre-1940s,” said the book’s author, Mary Hennen. She’s an assistant collections manager at the Field, and director of the Chicago Peregrine Program. “By the 1960s, they had been wiped out of that area.”

“On some level it’s very fitting working in a natural history museum that has an egg collection, because museum collections were pivotal in understanding what had been happening to the peregrine,” Hennen said. “Where you still had a few attempting to nest in the 1960s, scientists went and collected the crushed eggshells and compared them to the historic eggs that were in the museum collection.”

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That comparison led scientists to discover how the pesticide DDT inhibited calcium production in female peregrines, leading to thin shells that were crushed by the weight of adult birds incubating them. DDT was banned, the peregrine was added to the endangered species list, and captive breeding of the birds got underway. The Chicago Peregrine Program began its work in the mid-1980s. Today, Hennen says there are 30 to 35 pairs of peregrines around Illinois, 20 to 25 of which are in the Chicago area.

The book doesn’t just tell the story of the peregrine falcon’s recovery – it also shows how naturally cliff-dwelling birds have made a home in an urban environment.

“You sort of go, wow! But when you start to think about it, it totally makes sense to you. What is a city but a pseudo-cliff along a waterway? You have Lake Michigan, you have all these buildings with all these ledges … you have plenty of prey for them to feed on,” Hennen said. “On some level, that adaptability to the urban environment is part of the reason why it’s been such a quick recovery. You say 30 years, and it sounds like wow, you’ve been working a long time with these birds. But in the scheme of things, 30 years isn’t really that long.”

With a thriving population, Hennen says her job now isn’t just focused on recovery – it’s on helping humans coexist with birds of prey that make their home in the city.

The exhibition “The Peregrine Returns: The Art and Architecture of an Urban Raptor Recovery” opens Friday at the Field Museum and features the work of Hennen and Macnamara. Meet them both at a book signing at the Evanston Public Library on Thursday, June 29.

Below, an excerpt from “The Peregrine Returns.”

CHAPTER THREE: Reintroduction

SCIENTIST NOTE: My work with Peregrines began as the main hack site attendant during Illinois’ fourth year of release (1989). I lived at Illinois Beach State Park on Lake Michigan for four days each week. My day started at sunrise, when I left camp, climbed the hack tower, and fed the birds. It ended at dusk, when darkness fell and the birds were no longer visible. It was an amazing experience. Animal behavior is fascinating and I was spending more than forty hours a week watching young Peregrines.

One morning I watched for hours as Peregrines played in the surf. One would lie down on shore and let the waves wash over him. As a rolling action tumbled the falcon, it would stand, run up the beach returning to lie down again. Others joined in. Immature falcons acting like a bunch of kids frolicking in the surf. Being enveloped in the delight shown by the Peregrines, I was able to put aside any worry over the species to simply enjoy the show.

How were scientists able to bring back a species no longer found in the wild? It was not enough to ban DDT (which occurred in 1972) or place Peregrine Falcons on the Endangered Species List (1973). While those measures would help protect the few remaining Peregrines, it did nothing to restore them to areas where there were none.

Scientists with the Peregrine Fund (then based at Cornell University) developed a program of captive breeding and release, called hacking. The first two releases of Peregrines in the Midwest (near the Mississippi River) in 1978 and 1979 involved birds bred at the Cornell lab. Beyond that, with the exception of perhaps one more from Cornell, all of the birds released in the Midwest came from falconers turned breeders.

Illinois used hacking methods when the Chicago Peregrine Program joined the effort to reestablish Peregrines in the Midwest. Our goal was to have three nesting pairs in Illinois by 1990, the last year of release.

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The Chicago Peregrine Program began in 1985 as a cooperative effort of the Chicago Academy of Sciences, Lincoln Park Zoo, Illinois Department of Conservation, and Illinois Audubon Society. Its goal was to help restore Peregrines to Illinois and the Midwest. From 1986 to 1990, the Chicago Peregrine Program released a total of forty-six captive-bred Peregrines from four different hack sites.

In order to have young Peregrines to release into the wild, scientists first had to find a source of birds. They turned to falconers. By breeding their birds in captivity, falconers could supply scientists with fertile eggs and/or chicks. Eggs were hatched in incubators and the young chicks (called eyasses) were carefully raised to ensure the birds would stay wild and not imprint on people.

The Raptor Center in Minnesota coordinated the transfer of young Peregrines from breeders to the Chicago Peregrine Program. The young birds sent were approximately thirty-five days old, about a week younger than fledging age. They were placed in a specially designed box, called a hack box, located at a chosen release site.

One side of the hack box is a sliding barred door open to the air. When it is closed, young falcons can still observe their surroundings but not venture out. A “delayed feeder” allows hack attendants to feed the birds without being seen. Prior to release, young falcons are placed inside a back room with a trap door. While the birds are hidden, a two- to three-day supply of food is placed in the box and the front barred door is removed. Attendants back away from the hack box and the trap door is sprung. They are free.

Within the next couple of days the immature falcons will take their first flight. Care is taken to minimize the presence of humans so that birds are not prematurely startled into fledging. Over the following weeks, the Peregrines learn, on their own, to fly and hunt. As they begin catching their own prey, the young falcons return to the hack site less frequently. Exploratory flights become longer and longer, with the Peregrines eventually leaving the site entirely to find their way in the wild.

The goal of the Chicago Peregrine Program was to help reestablish Peregrines on a regional basis with a hope that some birds would breed in Illinois. The success of this plan can be seen in the dispersal of Peregrines across the Midwest and their subsequent breeding. Not only have Peregrines released or born in Illinois moved to neighboring states but their birds have come here. Illinois’ breeding adult Peregrines have originated from hack sites and eyries located in Illinois, Indiana, Minnesota, Iowa, Missouri, Ohio, Nebraska, Wisconsin, and Canada.

Reprinted with permission from The Peregrine Returns written by Mary Hennen and illustrated by Peggy Macnamara, published by The University of Chicago Press. Text  © 2017 by The University of Chicago Press. Paintings © 2017 by Peggy Macnamara. All rights reserved.


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