An unseen amount of bird deaths from window collisions occurred this week in Chicago, according to the Field Museum.

These preventable tragedies occur every year, especially during fall and spring migration, but this incident was noticeably worse. Nearly 1,000 birds died after striking the windows at McCormick Place convention center Thursday, “the most Field collecting efforts have documented in the past 40 years,” a post by the museum said.   

The incident has set Chicago’s birding community “abuzz,” reported WTTW, a PBS member television station in Chicago.

According to WWTW,  migrating birds were passing over some points of the city at a high-intensity rate of 100,000 that day amid adverse flying conditions. Both factors led to an overwhelming number of birds toward Chicago’s Lake Michigan beachfront along their harrowing journey.

Swarms of birds are flying over the US:Explore BirdCast's new migration tool to help you view them.

In addition to higher incidences of bird collisions, recent evidence has pin-pointed climate change’s impact on birds. Birds in both North and South America are getting smaller as the planet warms, and the smallest-bodied species are changing the fastest, according to previous USA TODAY reporting. 

According to the Field Museum, smaller bodies hold on to less heat and larger bodies hold on to more, which helps animals stay a comfortable temperature in different environments. Meanwhile, the birds’ wingspans may have increased so the birds are still able to make their long migrations, even with smaller bodies to produce the energy needed for flight, the Field Museum said.

Data from the Field Museum — collected by a team of scientists and volunteers who search for birds that collide into the center’s windows every day during the migration seasons — has been used in studies to make the case for more protections to make collisions less frequent to help vulnerable birds. 

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Here's what to do to help prevent bird deaths

According to Audubon Great Lakes, collisions with human-made structures are a leading cause of bird deaths in the United States, causing up to 1 billion bird deaths each year in North America. Evidence shows "the total number of birds in the sky on a given night and the direction of the wind both play a role in mortality, but the biggest determining factor was light," Field Museum said.

"It doesn't have to be this way," Audubon Magazine writes. "Though we might not be able to reverse human development, we can be proactive about preventing bird deaths that results from our man-made obstacles."

Groups including Audubon and BirdCast provide the following tips:

• Make your windows obvious to avoid confusing birds.
• Do not use landscape lighting to light up trees or gardens where birds may be resting.
• Close blinds at night to reduce the amount of light being emitted from windows
• Advocate for bird-safe building standards and show up to city meetings.

For more specific details on where to start in preventing bird collisions, visit Audubon Great Lakes' website.