Ann W. Richards Congress Avenue Bridge spans Lady Bird Lake between César Chávez St. and Barton Springs Rd. When engineers refurbished the bridge in 1980, they inadvertently created an ideal roost for migrating Mexican free-tailed bats. Today the underside of the bridge is home to what’s been called “the world’s largest urban bat colony,” which at its annual peak in August numbers as many as 1.5 million of the creatures.
Shortly after dusk each evening, swarms of bats flood out from the narrow crevices beneath the bridge to hunt for insects, a sight that attracts hundreds of spectators. A great spot for bat watching is the grassy area at the bridge’s southeast corner where visitors will also find several signs describing bat anatomy and why the bridge offers the perfect seasonal home for them.