Spring is around the corner, which means two things in Chicago: a wide variety of birds will soon pass through the area’s migratory corridor as they head north for the summer; and – less pleasant to consider – tens of thousands of rats will emerge from their winter shelters.

The city of Chicago spends more than $10 million annually to battle rats and staffs its Bureau of Rodent Control with more than 120 employees.

(Courtesy of the Field Museum)

(Courtesy of the Field Museum)

(Courtesy of the Field Museum)

(Courtesy of the Field Museum)

(Courtesy of the Field Museum)

(Courtesy of the Field Museum)

Ornithologist Pete Marra, the director of the Smithsonian Migratory Bird Center, and his colleagues at the Smithsonian published a study about such free-range cats.Marra called outdoor cats “as invasive and disruptive to native ecosystems as gypsy moths or West Nile Virus” in a Washington Post op-ed.

“We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually,” states the Smithsonian report.“Domestic cats … have been listed among the 100 worst non-native invasive species in the world. Free-ranging cats on islands have caused or contributed to 33 (14%) of the modern bird, mammal and reptile extinctions recorded by the International Union for Conservation of Nature (IUCN) Red List,” the study reveals.

Related stories:

Long-Eared Owls ‘Invade’ Chicago

Jan. 19: Why are there so many long-eared owls showing up in Chicago this winter? Bird watchers call it an “eruption.”

Dry Ice: Chicago’s New Weapon Against Rats

Sept. 20, 2016: Mayor Rahm Emanuel and the Department of Streets and Sanitation on Tuesday announced a pilot program that uses dry ice to curb rodent infestations

Cats and Rodent Control

May 13, 2014: Like most big cities, Chicago has a rat problem. Exterminators and local municipalities do their best to make a dent, but now there's a new approach to rodent control that is actually quite old.

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