Congress Avenue Bridge bat colony

The Congress Avenue Bridge hosts a large colony of Mexican free-tailed bats (Tadarida brasiliensis) that roost in the bridge’s underside; peak-season counts have been estimated in the hundreds of thousands to over a million individuals. The colony is considered the largest urban bat colony in North America and emerges nightly from spring through fall, creating a regular wildlife-urban boundary that is a popular public viewing event. The City of Austin manages interpretive programs and signage at the bridge to inform visitors about the bats and their habitat.