Chicago’s McCormick Place, the largest convention center in North America, was recently responsible for the deaths of at least 1,000 small birds that crashed into its thick glass walls.

According to the Chicago Bird Collision Monitors (CBCM), a volunteer conservation project dedicated to the protection of migratory birds, on October 5, the carcasses of at least 1,000 small birds, including  Tennessee warblers, hermit thrush, and American woodcocks were found around McCormick Place. They all died after colliding with the iconic building’s transparent glass walls, which birds simply cannot detect. The CBCM said that this was the highest number of crash-caused bird deaths that the group recorded from the grounds of one building in a single day. Unfortunately, the number of deaths may actually be much higher, because many birds continue to fly after suffering serious injuries only to die hours later.

Photo: aaron vansieleghem/Unsplash

“It’s the tip of an iceberg but it’s it’s a huge, huge amount of birds we found both dead and injured,” said Annette Prince, director of CBCM, adding that the mass death was a “very unusual and tragic occurrence”.

Experts estimate that around one billion birds die every year due to collisions with man-made buildings, with those covered in glass posing the biggest danger. However, recording at least 1,000 deaths around a single building, in just one day, is highly unusual. Douglas Stotz, a conservation ecologist at the Field Museum in Chicago told National Public Radio that “in one night we had a year’s worth of death”, adding that between 1,000 and 2,000 birds hit McCormick Place every year.

“Anywhere you’ve got glass, you’re gonna have birds hitting the windows,” said Bryan Lenz of the American Bird Conservancy, but in this particular case, the high number of deaths is also indicative of the unusually high number of birds flying in and around Chicago last week, most likely flying from Canada en route to South and Central America.

Unfortunately for the birds, McCormick Place was hosting an important event last week, which meant most of its lights were open, which only confused the animals even more. Studies have shown that light pollution is one of the main causes of bird collision with man-made obstacles and that shutting off half the lights in large buildings can reduce collisions by six to 11 times. To make matters worse, a storm passed over the city on Wednesday, forcing birds to fly lower and face an even greater risk of collision.

 

Bird tracking project Birdcast estimates that around 1.5 million birds were in flight above Cook County on the night of October 5, when McCormick Place recorded the highest number of bird deaths in its entire existence.