BALTIMORE, MD—The skies over Maryland will be busy on Monday night, but not with airplanes.

The Maryland Department of the Environment says that over 4 million migrant birds are expected to fly over the state tonight, with over 33,000 expected to pass over the Baltimore area.

According to BirdCast:

For those in areas under heavy migration advisories, this will be a great opportunity to experience nocturnal migration by listening at night to vocal birds in flight, or by observing the following morning for new arrival and departures. In the highly urbanized northeast, it is also particularly important to turn off lights at night to avoid attracting birds into hazardous conditions in which they can collide with buildings and other structures.

BirdCast has placed Maryland under a “high” Lights Out Alert for Monday night, as seen in the graphic below.

The site estimates that 405 million birds will take flight on Monday night across the lower 48 states, including 50 million birds in the northeast alone. This will likely represent one of the largest migration nights of the year in this region.

More in the charts below.

4.1 million birds are forecast to pass over Maryland tonight! Please consider turning off outside lights tonight to make the birds’ journey a little easier. For more information visit: https://t.co/OrgMnWkd5m#birdmigration #lightsout #birdsinflight pic.twitter.com/C9DliWblcG

— MD Environment (@MDEnvironment) September 14, 2020