The bats start to make an appearance in early March and stay until November, leaving to hunt only when the sun sets. When they first arrive in spring, the estimated number of the bats is between 750,000 to 1.5 million! When the colony is out, they consume as many as 20,000 pounds of insects before returning to the South Congress Bridge. Once it starts to get cold in November, many begin their trek back to their original home in Central Mexico.
In late July and early August are best because that is when the whole colony goes hunting. Imagine witnessing 1 million bats flying away from the bridge!
Between April and May, the mothers are still expecting their pups—actual names for newly born bats— they tend to be hungry and are great nights to visit as well.