Austin, Texas: Holy Bat…

One of nature’s most amazing spectacles is the emergence at dusk of about 750,000 Mexican Free-tail Bats. Even more remarkable is that since they began roosting under the Congress Avenue Bridge in the mid 1980’s it has become not only Austin’s main tourist attraction but North America’s largest urban bat colony.

Most of the colony is female. They begin returning from Central Mexico in mid March, already pregnant, and are due to give birth to a single pup in the coming weeks. As many as 200 bats roost in a square foot amongst the narrow cervices under the bridge. By late summer the numbers will be staggering with over 1.5 million, almost double that of the human population in Austin! Once the cold fronts begin in late October they head south to a warmer winter.

My brother Gordon and I joined about a thousand people last night to experience this nightly ritual. While some watched from both sides of Lady Bird Lake others choose to look down from the bridge while others had views from a river boat. At 8:01 a Common Nighthawk called as it flew over the bridge and the bats began to stream out, all heading in one direction – east. By the time they return at dawn they will have consumed between 5 and 15 tons of insects!

For about 30 minutes we watched as streams poured out, snaking their way like a wisp of smoke into the countryside. One amazing sight was a Green Heron that caused some commotion as it flew into the the bats appearing to pick one off. By 8:35 flocks of city grackles and starlings headed to roost and it was getting tougher to see the bats. The shear number of bats would no doubt continue to emerge for well over another hour, and tomorrow, they will do this all over again.