Peregrine falcons attack bystanders in downtown Chicago

High above the heads of business professionals gathering for lunch downtown Thursday, the tail feathers of a peregrine falcon popped out over a concrete ledge on a large building.

Joe Bisognani, who works for Wabtec, a technology company across the street in the Loop, stood on the Monroe Street Bridge, squinting up at the tiny shadow protruding in the sky. The Palatine resident said he heard about the falcon in the news.

“I thought about taking a different route, but this was on the way to getting my afternoon coffee and I was willing to take the risk of being in the falcon’s territory,” he said as he strategically placed himself behind a post to avoid a potential attack.

Since last Friday, there have been multiple instances of birds swooping down and hitting pedestrians walking along the Chicago River, according to people who work nearby. “Warning! Beware of falcons, parents will attack to protect babies on building ledge. Take a different path,” read laminated signs on both sides of a building.

These birds of prey are just trying to protect their young from a potential threat, said Mary Hennen, director of the Chicago Peregrine Program at the Field Museum.

Hennen said peregrine falcons lay eggs at the beginning of April and incubate them for about a month. During nesting season, they typically don’t bother anyone. But as soon as their eggs hatch, they go into full defensive mode.

“Some peregrines are more defensive than others,” she said.

The falcon, named Stormy, according to Hennen, flew in a slow, elegant circle, spreading its wings Thursday. It perched on a tall black building across the river later in the afternoon.

Hennen has put a tracking band on Stormy, so she knows a lot about the bird’s story. The falcon has been nesting on this particular building since 2016, but on a different side and a few stories up. The falcon’s nest is on the seventh floor, according to building staff.

In a week, Stormy’s three chicks will embark on their “fledgling” or first flight, dropping onto ledges below the nest.

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Hennen said there were almost no peregrines nesting in Illinois from 1951 to 1987. In the 1960s, falcon populations plummeted due to pesticides such as DDT that thinned their eggshells.

Falcon populations have completely revived in recent decades, partly due to their ability to nest on the ledges of tall buildings, said Hennen. In 1988, the Tribune reported the sighting of a nest on top of Sears Tower. The American peregrine falcon was removed from the endangered species list in 1999.

“It’s really not any different than being on a cliff ledge to them,” she said. “The majority of our Midwest (falcon) population is in the urban environment.”

Stormy is a middle-aged peregrine, according to Hennen. This is Hennen’s 35th year working with the species, and she said she’s obsessed. They’re aerial predators, she said, diving 200-mph for dinner in a process called “stooping.” They have no predator.

“They’re tremendous birds,” she said. “Their color patterns alone.”

Most of the swooping that has occurred recently is not done to make contact, said Hennen, but is an intimidation technique. The falcon just wants people walking around near the nest to go away.

But the intimidation tactics didn’t seem to be working Thursday afternoon. Business professionals and families stopped to read the warning sign, but proceeded to stretch their legs along the river. Groups gathered at tables outside South Branch Tavern and Grille, munching on fries and Caesar salad.

Scott Hoyne, a retired lawyer, walked along the river to meet a friend for lunch. He saw the sign and looked up.

“The sign is there for a reason. I never imagined it would attack people, but I guess they do,” he said. “You’d think we’d scare them.”

Austin Akerlund, an employee at South Branch, said heads turned as falcons swooped last week.

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“They (the falcons) were going crazy. You can see the evidence on the ground now,” he said, pointing to droppings on the concrete.

A lot of buildings in Chicago have peregrine nests. Hennen has created a website to map where they are around the state. She instructed anyone who has found a fallen peregrine to report it to Chicago Bird Collision Monitors, a nonprofit dedicated to the respite and protection of migratory birds through daily rescue efforts.

Laura Chambers also works across the street and heard about the bird in the news. She said she came down from her office across the street a few times to try to catch sight of the bird.

“We understand why it’s attacking people. It’s protecting its babies,” she said. “I’m surprised they’re still seating people at the restaurant. I’m avoiding that path.”

At one point in the afternoon, the falcon tucked its wings in and dove in a stunning free fall as unassuming pedestrians walked in the river corridor below.

nsalzman@chicagotribune.com