Chicago building kills 1,000 birds in one day


At least 1,000 migrating birds died after colliding with a building in Chicago on 5 October.

Volunteers recovered the carcasses of the migrant birds within a 2.4-km radius of McCormick Place, the largest convention venue in North America. The building is mostly covered with glass.

The event involved the highest number of bird deaths from a single building in one day. Tennessee Warbler, Hermit Thrush and American Woodcock were among the species involved in the mass deaths. 

Bright lights, glass buildings and a busy night for bird migration combined to cause the worst 24-hour period for bird strikes Chicago has ever seen (Don Sniegowski via Flickr).

The event involved the highest number of bird deaths from a single building in one day. Between the evening of 4 October and the next morning, a peak estimate of 1.5 million migrant birds flew over Cook County, in which Chicago is situated.

Annette Prince, director of Chicago Bird Collision Monitors, said: "It's the tip of an iceberg but it’s a huge, huge amount of birds we found both dead and injured."

Brendon Samuels, who studies bird collisions at the University of Western Ontario, said: "Not every bird that hits the window is going to leave a body.

"In fact, we often see birds collide with glass and they continue flying some distance away, seriously injured in ways that ultimately they won’t survive past a few hours."

Light pollution from cities can attract migrating birds at night, which leads to window collisions far and wide in the US.

Up to a billion birds are thought to be killed in window collisions each year. Chicago is the worst city in the US for bird collisions with buildings.

In 2021, a study at McCormick Place found that turning off half of the lights can reduce collisions by up to 11 times. The building is part of a voluntary program called 'Lights Out Chicago', which encourages the switching off or dimming of lights unless people are inside.

A representative from McCormick Place said that there was an event taking place on site during the week, meaning the lights have been on.