Last Thursday night, members of the Natural History Society of Maryland gathered to watch a pretty amazing spectacle.

Thousands of chimney swifts, a type of migratory bird on its way to winter in South America, gathered to roost in a building across the street from the group's headquarters at 6908 Belair Road in Overlea.

Having watched the birds for a couple of days, the naturalist group hosted a party Thursday to watch them swirl and swarm down the nearby chimney, then posted this video of the event to Facebook.

The quality of the video isn't great, but each moving dot in the background is a bird headed down the chimney to roost for the night. Check out the video, originally posted to the group's Facebook page, posted above.

Have you ever seen a large flock of birds like this in the area? Tell us in the comments.