each year when my friends and I get together, we try to do quirky things in the city we visit, in addition to more traditionally touristy stuff. I’m not sure where on the spectrum visiting the Congress Avenue bat colony falls … quirky for sure, but also very popular! the colony consists of between 750,000 and a million and a half Mexican free-tailed bats; they summer in Austin and migrate to Mexico for the winter. 
for all appearances, the bridge doesn’t seem terribly special; three lanes in each direction over Lady Bird Lake in a spot that has hosted a bridge since the early 1870s (a pontoon toll bridge). the City of Austin assumed complete responsibility over the (newer, iron) bridge in the late 1880s, which they were forced to repair several times over the subsequent two decades. by 1908, increase in traffic demanded the construction of a newer, wider bridge and a proposal for the current concrete span bridge were drawn up. at 910 feet it includes six spans which rise to 45 feet above ground; it opened on April 4, 1910.
the bats came to live under the bridge following refurbishment that occurred in 1980. there are fifteen crevices beneath the roadbed, each about 17 inches deep, which appealed to the bats and offered about 14,000 feet of potential habitat. the bats emerge from their roosts each dusk to search for food, swarming out towards the east for 10 or 20 minutes. tourists congregate on the bridge’s sidewalks, in the parking lot of the Austin-American Statesman, and on boats in Lady Bird Lake. we opted to stand on the sidewalk (near a family with two young boys calling out to the bats “hey, bats, come out so we can see you!”), but saw a fair few people out on water bikes, kayaks, stand-up paddleboards, paddle boats, canoes, and one paddling swan. we ended up waiting about an hour before the bats emerged, but in the interim the sunset off to the west provided a remarkable diversion .
