GRAND RAPIDS, Mich. (WOOD) — Check your feeder! Warm weather this week is forecasted to help as many as 447 million birds migrate back north across the eastern United States, according to the Cornell Lab of Ornithology.

Every spring and fall, billions of birds migrate across the United States. Perfect conditions can spark mass-migration events.

In Michigan, the bird migration is the highest it has been all year. According to BirdCast, more than three million birds migrated across Kent County, Michigan, between the evening of May 10 to the morning of May 11. These estimates are done using nocturnal weather radar imagery, which can detect birds in flight. Songbirds migrate at 500 to 2,500 feet in elevation. Waterfoul migrate at 200 to 4,000 feet above the ground.


One of the hazards for migrating birds can be artificial light, also known as light pollution. Migration around cities can be especially difficult because of all the human-made light, which can disorient, confuse and exhaust traveling birds on their journey. This, in turn, can lead to more bird deaths due to increased fatigue and collision.

Each year, buildings are the cause of about 340 million bird deaths. Residences are responsible for 253 million bird deaths. Wind turbines, in contrast, claim 6.6 million (100,000 times less than buildings).

The Cornell Lab of Ornithology urges locals to leave their lights out on mass-migration nights, to help the birds make it to their final destination safely. Turning off unnecessary lights, or at least dimming them, can help birds complete their journey safely. According to the Cornell Lab of Ornithology, 447 million birds were expected to migrate across the U.S. Wednesday night, with another 446 million expected Thursday night and 369 million Friday night.