Illinois residents urged to turn off lights to help migrating birds. Here's when

Millions of birds crossed over Illinois overnight in their spring migration, and “Migration Alerts” are active as those flights will continue.

According to Birdcast, more than 22 million birds crossed over the state of Illinois Sunday night and into Monday morning, with up to 35.5 million birds in flight just after 1 a.m. Monday.

In Cook County alone, more than 2 million birds crossed county lines, and it’s expected that the crossings will continue in earnest this week.

As millions of birds continue visiting the Chicago area, here are some steps that residents can take to keep them safe.

When do birds typically migrate?

Peak migration for birds over the state of Illinois occurs in mid-to-late May, with hundreds of different species heading north for the summer breeding season.

Those migration flights for songbirds and other species typically take place in the overnight hours. According to experts, birds typically take flight 30-to-45 minutes after sunset, with the greatest number of birds in flight typically seen approximately two-to-three hours later.

When should residents turn lights off?

One of the best ways to help protect birds is to turn off lights during peak migration times.

According to Birdcast, the best time to turn off or dim exterior lights and interior lights is between the hours of 11 p.m. and 6 a.m., when most birds are active.

Bright lights can disorient and attract birds, making them vulnerable to collisions and to predators on the ground, according to the website.

Hundreds of millions of birds are killed each year in collisions with buildings, and residents and businesses are being asked to do their part to keep the creatures safe.

In addition to turning off unneeded exterior lights, residents and businesses are also asked to dim or turn off lights in lobbies, and to draw blinds to help keep light from escaping through windows.

Finally, exterior lights should be aimed downward and be well-shielded so that birds aren’t attracted to them.

Are there other steps?

Another key step in protecting birds is to bring pet cats inside during overnight hours.

According to the American Bird Conservancy, cats kill an estimated 2.4 billion birds in the United States every year, and during migration season those impacts can be even more devastating, as exhausted birds typically seek refuge in plants and trees to rest on their journeys, making them vulnerable to attack.

Since cats like to hunt at night, active migrating birds can be a target, leading to experts asking residents to keep animals inside when possible.

How many birds typically cross Illinois?

According to Birdcast, more than 359 million birds have already crossed over Illinois on their way north, with hundreds of millions more expected to do so in coming weeks.

Spring migration typically begins to subside in early-to-mid June, with the peak season occurring in the later stages of May.

Between 10 p.m. Sunday and 6 a.m. Monday alone, more than 22.8 million birds crossed over Illinois state lines, with 2.6 million of those birds crossing over Cook County.

American Redstarts, Magnolia Warblers, Baltimore Orioles and Eastern Wood-Pewees are among the birds currently flying over the state.