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All About Austin’s South Congress Bridge Bats

Aug 10th, 2022

If you’ve spent any time at all in Austin, then you’re sure to have heard about the bat colony living under the South Congress Bridge, just a few blocks south of the Texas State Capitol. 

These bats form one of the largest colonies in North America, and their nightly exodus into the sunset is a wonder that attracts visitors from all over the region.

Here’s all you need to know about the Congress Bridge bats and how to see them!

How to see the bats under Congress Bridge & Lady Bird Lake

A bit about the bats

The bats that flood out from under South Congress Bridge number in the tens of thousands, and bat enthusiasts in Austin can see up to 1.5 million of them pour out from the bridge in the spring and summer months. Around 100,000 live there year ‘round.

The Mexican free-tailed bat, also known as the Brazilian free-tailed bat, is not only one of the most abundant bats on the continent, but one of the most abundant mammals in general! That being said, these bats live in relatively few colonies numbering millions of bats, leaving the plentiful species vulnerable to habitat loss due to human interference. 

These colonies can be found anywhere from the southern half of the United States through to the center of Argentina in South America, where they roost in caves, empty buildings and, of course, under bridges! Not all of these bats migrate, but the ones that do usually migrate en masse from the Southwestern U.S. to Baja California, or from the Midwestern U.S. to South Texas and Mexico.  

Texas is home to a few of these large colonies, the largest being Bracken Cave outside San Antonio which is home to up to 20 million bats! The largest urban bat population is right here under the South Congress Bridge over Lady Bird Lake, making Austin a crucially important habitat for the protection of the species as a whole. 

Fun facts about the Mexican free-tailed bat

  • The Mexican free-tailed bat is one of the fastest mammals on the planet, with a study showing a recorded speed of 160 miles per hour!
  • This species of bat can live up to 18 years!
  • The colony here in Austin eats anywhere from 10,000 to 30,000 pounds of insects each night, so thank these guys for keeping the bugs to a minimum when walking around the lake!
  • These bats fly up to two miles above the ground, all the while using echolocation to locate insects below them on the ground.
  • During peak season, viewers can see columns of bats up to a mile in length pouring out from the bridge!

How to see the South Congress Bridge bats

Bats are nocturnal animals, of course, so it can be tricky to see the grand exodus since it usually occurs after dark. But there are a few ways you can predict how and when to see the bats on a typical night.

Emergences, as they’re called, happen in the spring and summer months. The first emergences occur during mid March to late April during the spring migrations, and the second happens from late July through August when the young are just learning to fly. The bats fly every night during these periods, so aim to check them out during these months!

The bats will emerge from the bridge within thirty minutes of sundown, giving viewers up to an hour of time to watch and wait. If the weather is hotter and drier, then the bats usually emerge earlier in order to hunt for the more scarce supply of insects. If the weather is cooler and more humid, the bats can afford to wait until well after dark to do their nightly hunts. 

The best times to see the spectacle, then, is on nights that are hotter and drier, as the setting sun will silhouette the flying colony beautifully against the Austin sunset. 

If you do go on a cooler night or on a night during spring migrations, then the best place to view the bats is from right underneath the bridge. From there, you can look up toward the streetlight spilling from above and see the flicker of bats passing through the beams from under the bridge. 

What not to do when watching the bats

Bats are sensitive creatures and are easily disoriented by lights and sounds. Here are some tips for what not to do when watching the South Congress Bridge bats!

  • Do not: shine white lights onto the bats as they fly from the bridge.
  • Do not: capture or handle the bats. 
  • Do not: use drones or other flying objects around the bridge around the mergence. The drones could collide with the bats and kill them. 
  • Do not: make loud noises or play any music or instruments within 100 feet of the bridge, as bats rely on echolocation to hunt and navigate. This includes clapping and whistling!

So, if you live in our Austin apartments, especially our South Shore apartments on Lady Bird Lake, then checking out this magnificent natural wonder is a must during your time in Austin! If you keep an eye on the weather, the season and the time, then you’re sure to see the South Congress Bridge bat colony in its finest form!


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Featured photo courtesy Pixabay/jameswcaras

Author of Article

Colleen Ford is a South African who now lives in Spokane, Washington. She loves to travel, camp (in warm weather) and bake.

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