Residents and tourists are gathering each night near Congress Street Bridge in downtown Austin, Texas, to watch some 1.5 million bats form a black cloud so large that it shows up on local weather radar, Reuters reported.

The bats have been finding habitat under the bridge since the 1980s when they moved to Austin looking for food, according to experts.

Central Texas is the world’s largest habitat for bats with over 100 million of them residing here. These bats living below the bridge in Austin apparently form the largest urban bat colony in the world.

A recent drought in Texas has destroyed crops in Texas and killed delicious pests that the Mexican free-tailed bats eat. This has forced bats to make their nightly flight for food earlier than usual each night, giving the locals more time to watch the normally-nocturnal critters fly before the sun goes down.

Start the slideshow to view the nocturnal creatures in Austin.