Congress Avenue Bridge bat emergence

Each spring and summer, Mexican free-tailed bats roost beneath the Congress Avenue Bridge and emerge nightly at dusk in a large, visible column; the phenomenon draws thousands of spectators and is frequently mentioned in local guides. Estimates of the summer population vary by year and by survey method, with counts commonly described in local news and wildlife reports as ranging from several hundred thousand to over a million bats. The bridge colony is widely cited as one of the largest urban bat colonies in North America and figures prominently in Austin's cultural identity and folklore. Observations and population estimates are based on scientific surveys and long-term monitoring, while some anecdotal stories about the bats have entered local legend.