On the Road in Texas - Mexican Free-tailed Bats

Texans like to say that they do everything big. So, it is no surprise that in the Texas state capital of Austin you will find the largest urban colony of bats in the world.
Nearly 1.5 million Mexican free-tailed bats live under the Congress Ave. Bridge that crosses the Colorado River in downtown Austin.
Each day as the sun fades on the western horizon, the bats come out to travel as much as 125 miles and to consume 20,000 pounds of insects. Initially viewed as pests by the residents of Austin, the bats later became recognized for their ability to help farmers by consuming their nightly load of insects. Still later, Texas named these Mexican free-tailed bats as the state mammal.
These photos are of minimal quality - basically I got directly under the bridge, pointed the camera straight up, and let the flash and auto focus do the rest. The strobe flash allowed us to actually see the bats while we where there.
The bats spend their days tucked away in the 1-2 inch spaces between the concrete parts of the bridge (note the dark stains from the bats). Each bat is about the size of typical field mouse. As you can see from the first three photos, every 15 seconds or so nearly a dozen bats drop out of the spaces and begin to fly away.
If you look closely at the fourth photo, you'll see the flash reflection from the flying bat's eyes. If you look very closely (click on the photo to get an enlarged view), you'll see at least another dozen bats still tucked in the space with the flash reflected in their eyes as well.
In this last photo, you can see that on the night we visited the bat colony, it was quite dark when the the bats emerged. This last photo was taken across the river with the bridge in the lower, foreground.