Every summer night, thousands of people gather to see the world's largest urban bat colony emerge from under the Congress Avenue Bridge.
With up to 1.5 million bats spiraling into the summer skies, Austin now has one of the most unusual and fascinating tourist attractions anywhere.
It is estimated that more than 100,000 people visit the bridge to witness the bat flight, generating ten million dollars
in tourism revenue annually. Austin's bridge bats are Mexican free-tailed bats. They migrate each spring from central Mexico to various
roosting sites throughout the southwestern U.S. Most of the colony is female, and in June each one gives birth to a single baby bat, called a pup.