Bat Colony at Congress Avenue Bridge
Each day in downtown Austin, hundreds of drivers, cyclists and
pedestrians cross the Congress Avenue Bridge
over Town Lake.
Underneath them, from April through October, an estimated 1.5 million Mexican free-tailed bats quietly roost, poised for their
daily sunset exodus into the Austin nighttime sky. Altogether, the nocturnal wonders make up
the largest urban bat colony in North America and are one of Austin’s most popular attractions.
Each year in late February, approximately 100 million Mexican free-tailed bats (Tadarida
brasiliensis) migrate from Mexico to Central Texas. The mammals, mostly female, congregate
in various roosting spots during the summer months to give birth and raise their pups.
The bats shadow the Austin sky as they emerge from under the bridge at dusk each
night in search of food. The most dramatic exoduses occur in August when the weather is hot
and dry, and the free-tailed pups set out with their mothers for the first time in search of food.
The bats are among the world’s most fascinating mammals. During their migration, they
fly up to two miles high in the stratosphere’s wind currents. Here they can reach speeds of up
to 60 miles per hour, allowing the group to migrate from Mexico to Austin in only one night. The
bats consume an estimated 10,000 to 30,000 pounds of insects nightly (2-7 million pounds of
bugs per year), making them extremely valuable as a source of pest control for the area.
Austin’s batty phenomenon began in 1980 when engineers reconstructed the downtown
Congress Avenue Bridge. In the process, they made the crevices on the bridge’s underside
larger, unknowingly creating a perfect bat roost. Although bats had lived there for years, it came
as a surprise when they suddenly began moving in by the thousands. As the city came to
appreciate its bats, the population under the Congress Avenue Bridge grew to be the largest
urban bat colony in North America.
Austin offers several great spots for bat viewing. The nearby Austin American-Statesman bat observation area features educational kiosks, manned by interpreters from
Austin-based Bat Conservation International (BCI), positioned throughout the viewing area,
Thursday through Sunday during the summer.
Bat-watchers can also float Town Lake on nightly cruises offered by Capital Cruises and Lone Star Riverboat.
Local restaurants and hotels on the banks of Town Lake also provide prime vantage points.
To find out flight times, call the Austin American Statesman’s Bat Hotline at 512-416-
5700, ext. 3636. More information about the Congress Avenue colony is available from BCI at
P.O. Box 162603, Austin, TX 78716; toll-free 800-538-BATS; or www.batcon.org.