Mary and the Peregrines

Mary Hennen loves teaching people about animals, especially birds. She helps manage the Bird Collection at the Field Museum in Chicago, Illinois. The museum collection does not include live birds, but it does have more than 500,000 bird feathers, bones, eggs, and more. Some of the items are very old. Scientists study them to learn more about — and help — living birds. One bird that the collection helped is the peregrine falcon.

When Mary was a kid, there were no peregrine falcons in Illinois and hardly any in the rest of the country. At that time, many farmers used a bug killer called DDT to help crops grow. They didn’t know that DDT hurt birds. But people noticed that there were fewer peregrine falcons each year.

Scientists compared eggshells from new peregrine nests with old eggshells in the Field Museum collection. They learned that DDT caused the new eggshells to be very thin. When a mother falcon sat on her eggs — crack! — the shells broke. No baby birds were hatching.

The United States soon passed a law to protect the peregrine falcons and other endangered animals. Farmers stopped using DDT. Scientists learned how to hatch the thin peregrine eggs safely in nurseries and release the grown birds back into the wild.

But the scientists got a big surprise. Two of the peregrines they released chose to nest in downtown Chicago! Usually, peregrine falcons nest on the sides of cliffs, where great horned owls sometimes attack the nests. The falcons must have thought the city skyscrapers were like cliffs—but better, because there were no owls.

Mary got a job watching the peregrines. She wrote down what they did each day, so the scientists could see how well the peregrines did living wild in the city.

Mary loved watching the birds so much, she decided to spend her life helping peregrines! Now, when she’s not working at the museum, she directs the Chicago Peregrine Program, a volunteer group that helps these special birds.

Mary and other volunteers keep track of where each peregrine in Illinois lives, hunts, and builds a nest. They do this by putting a small metal bracelet, or band, around the bird’s leg.

Each band is stamped with a different number. When someone spots a bird and reads the band, researchers know exactly which falcon it is.

Thanks to Mary and other falcon watchers, we know that the peregrines still love living in downtown Chicago. Today, dozens of pairs of falcons nest in and near Chicago. That means part of Mary’s job is talking to people who wake up to discover that peregrine falcons have laid eggs on their balcony!

Having peregrine falcons for neighbors can be alarming. They are messy eaters and poop everywhere. They chase anyone who gets too close to their chicks, and they make a lot of noise. But Mary teaches people how to respect and enjoy their peregrine neighbors.

You don’t have to have a peregrine nest on your porch to watch these amazing birds grow up. Mary and her team installed tiny cameras in some of the nests so people everywhere can watch peregrine chicks grow up each summer. Have fun watching!