Congress Avenue Bridge Mexican free-tailed bat colony

The underside of the Congress Avenue Bridge in downtown Austin hosts a large colony of Mexican free-tailed bats that emerges at dusk from spring through fall. Estimates of the colony size have reached up to around 1.5 million bats in some years, making it one of the largest urban bat colonies in North America. The nightly emergence has become a documented natural phenomenon and a major seasonal attraction in Austin.