A spike in rat sightings in Lincoln Park is leading to requests from residents to the Tree House Humane Society to provide feral cats. Its manager Paul Nickerson says it used to get a few requests a week for the cats. Now it’s up to about 15 per day. But Steve Sullivan, Curator of Urban Ecology for the Chicago Academy of Sciences at the Peggy Notebaert Nature Museum, says rats aren’t the only creatures in the cats’ crosshairs. He says Chicago is an amazing migratory bird hotspot with more than 300 birds species flying through the area. Some include warblers, thrushes, bluebirds, blue jays, Baltimore orioles and more. Sullivan says they’ll be preyed upon.

“They’re flying into our neighborhoods looking for a place to rest, a place to feed. And suddenly out of the bushes, springs a cat that kills it,” Sullivan said. “And there’s never any knowledge of the environment built up.”

Sullivan says because rats are residents “they’ll figure out the behavior patterns of the cats, they’ll figure out when the cats are active and inactive and the rat’s will adjust their schedule to account for the cat’s presence.”

That means a disruption of neighborhood ecosystems.

“We will be simultaneously be eliminating the biodiversity of birds from our backyards,”
said Sullivan, adding that the cats could affect invasive insects eaten by birds like the cuckoo.

“It’s one of the few species that can eat that pest,” he said. “If the cat has access to that cuckoo, it will simply kill that cuckoo.”

And that would mean more, just different, pests.

Sullivan says one the best ways to control rats is to secure food sources like garbage cans.

Yolanda Perdomo is a reporter at WBEZ. Follower her at @yolandanews.