Austin, Texas, is home to the world’s largest urban bat colony, and just after sunset each evening in March, hundreds of thousands of the winged creatures emerge from beneath a bridge to soar into the night across Lady Bird Lake. Mexican free-tailed bats have been migrating to the city for hundreds of years, but it wasn’t until a 1980 expansion of the Congress Avenue Bridge that the numbers really took off. The renovation resulted in deep, dark, concrete crevices that roosting bats find ideal for raising their young. Now, the bridge serves as a nursery, hosting as many as 1.5 million bats each year. When the weather cools between October and November, the colony takes off again for warmer climes.
