Austin Advent -- Bats at the Congress Street Bridge

Another time-sensitive activity: watching the bats emerge at dusk at the Congress Street bridge. Alas, no bats in March. Why not? In early March, they are still hibernating. Lazy bats.

the blur in the middle is bats 

yes. stand on the bridge, like these people. 

if you stand below the bridge...
BRING AN UMBRELLA!
do I need to explain why?

Here is some verbiage from the Video City Guide

About Congress Bridge Bats Austin

The Congress Avenue Bridge spans Town Lake in downtown Austin and is home to the largest urban bat colony in North America.  The colony is estimated at 1.5 million Mexican free-tail bats.   Each night from mid-March to November, the bats emerge from under the bridge at dusk to blanket the sky as they head out to forage for food.  This event has become one of the most spectacular and unusual tourist attractions in Texas.  The most spectacular bat flights are during hot, dry August nights, when multiple columns of bats emerge.  There are several points from which to view the event, and an information kiosk is located on the north bank of the river, just east of the bridge.
More - caution! link has audio!!!