Bat colony flies back home to Austin

Congress Avenue bridge. (David Yeomans/KXAN)

AUSTIN (KXAN) — The bat colony that makes the Congress Avenue Bridge famous is repopulating.

The group of Mexican free-tailed bats is returning from their yearly migration just in time for South by Southwest visitors.

“We heard that there’s a bat colony that lives there,” said John Banker, who was visiting Austin from Canada.

“I mean, you guys are famous for that,” said Michael Terry, another SXSW visitor. “You have t-shirts, you have buttons, I mean it’s a big deal for Austin, right?”

“You know, the first time I saw them it just looked like smoke in the sky,” Austin resident Kara Remme said. “I thought it was really beautiful.”

After months spent in warmer climates escaping the cold temperatures that occasionally plague Austin during the winter, the time of year when you can see the world’s largest urban bat colony take to the skies at sunset is returning.

“Right now, the bats aren’t all back,” Shanna Weisfeld of Bat Conservation International said. “Most of them are still in Mexico, so there are maybe a quarter of a million [bats]. They’re coming in waves right now.”

While Austin residents are more than familiar with the colony of bats under the Congress Bridge, there may be something you don’t know about them.

“When the bats migrate back up north, all the females are pretty much pregnant after they’ve been mating,” Weisfeld said. “They come here, and this is where they have their babies.”

By mid to late-summer, the cracks on the underside of the Congress Bridge will be home to 1.5 million moms.

“Wow… that’s a lot,” Austin resident Brandon Ortiz said.

“Well, as a pregnant lady with a stroller, I think they’re welcome here,” Remme said.

Visitors and residents alike agree that the unusual attraction makes this place feel more like home.

“It definitely makes Austin unique,” Weisfeld said. “And people have embraced it. I mean, it’s ‘Keep Austin Weird.’”

The bat colony under the bridge first populated in 1980. When the bridge was rebuilt and widened that year, the intentional cracks in the construction provided what experts call a “perfect breeding ground” for the mammal.

Each night just after sunset, the Mexican Free-Tailed bats fly to farmlands up to 50 miles east of Austin to eat 20,000 tons of bugs.

Also responsible for pollinating the agave plant in regions farther south, bats make the production of tequila possible.

Mexican Free-Tailed bats weigh the equivalent of only two quarters, fly at up to 10,000 feet altitude, and achieve speeds of 60 miles per hour. provides commenting to allow for constructive discussion on the stories we cover. In order to comment here, you acknowledge you have read and agreed to our Terms of Service. Users who violate these terms, including use of vulgar language or racial slurs, will be banned. If you see an inappropriate comment, please flag it for our moderators to review.

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