I booked a boat tour to see the Congress Avenue Bridge bats in April because I’m a planner. But when it comes to Texas weather forecasts, you plan and God laughs. Spring could mean blue skies, soaring temperatures, high winds, storms and hail, sometimes all in a single day. So I kept an eye on my iPhone weather app. A week before boarding, the sun icons all disappeared under a row of gray thunderclouds and I began to worry. The bats wouldn’t come out from under bridge unless it was totally dry.

The day of the tour, I carried my umbrella like a talisman to Lady Bird Lake, muttering expletives like spells to bring back the sun. Two hours before the bats’ emergence the skies cleared. The sudden clearing felt frankly supernatural, a little like the bats themselves. Known as Mexican free-tails, they fly north from cave roosts in Mexico and Central America. It’s only the females who migrate, though: no bigger than two thumbs joined side by side, the bats arrive pregnant with one pup each. The free-tails form one glorious, chattering girl’s-only club until they give birth. After that the colony doubles in size from 750,000 to 1.5 million and includes a minority population of juvenile males.

Free-tail migration existed long before there was ever a Texas. And the bats didn’t gather in Austin in such concentrated numbers until after the Congress Avenue Bridge was renovated in 1980. At that time, engineers installed a deck support system scored by a series of horizontal slits. The bats discovered the darkness and safety the slits provided and their numbers exploded. They now constitute the world’s largest urban bat colony, though I prefer the term “bat cauldron.” It’s nothing short of uncanny that female bats found a home under a bridge that also happens to be named after Anne Richards, the only woman governor in Texas history. If witchery—and the power and magic it implies—has a gender, it most certainly must be female.

These days residents and tourists have nothing but love for the tiny flying mammals that transformed Austin into the bat capital of the world. The story was far different when the creatures transformed the bridge into a roost in the early 80s. Many Austinites called for extermination because they believed bats attacked humans. Media sensationalism didn’t help. One Austin American-Statesman headline from September 1984 read “Bat Colony Sinks Teeth Into City.” Dracula’s minions had arrived.

Biologist Merlin Tuttle knew better. A crusader for the rights of the Congress Avenue Bridge bats, he made it his business to educate people that free-tails had no intention of draining the life blood of innocent Austinites. Bats, he pointed out, consumed pests like beetles, moths and mosquitos; they also served a crucial ecological role as pollinators. Slowly, people listened; and the irrational fear that had overtaken the city turned to ash like a vampire caught at sunrise.

People who’ve seen the spectacle have told me that all you have to do is stand at the Congress Avenue Bridge railing and wait until five minutes after sunset for the bats. They never mentioned how bodies—too many of them—crowded for viewing spots that could be dodgy, especially during the smaller spring emergences. Common sense told me differently: get on the river, the view’s bound to be better from there. I was right: bats emerge from under the bridge, chattering as they spiral down from each of what our tour guide called “neighborhoods” before heading east towards the greenbelt zones. None of this is especially easy to observe at night from the top of the bridge. On the water I could savor the pleasure of free-tails pouring into the night like smoke, engaged and awed by a spectacle our pilot enhanced with infrared lighting.

Ten minutes later our boat headed for the dock. My brain whirred; I needed to make sense of what I had seen. What it all meant for me. Native Americans believe bats, with their echolocation abilities, are guides through darkness and symbols of death/rebirth. I didn’t need guidance through any dark night of the soul; I’d had my midlife crisis years ago. But in the span of a few short years, a great deal had changed for me. I’d left one profession for another. Moved house. And much as I didn’t want to admit it, begun to age.

The bats and I were female. But they possessed a fertility I no longer had and a vigor made me aware of how much I enjoyed taking my time. Cosmic esoterica only reinforced the emblems that came with living into a sixth decade. I was in my second Saturn return, give or take a few degrees. That transition was about wisdom. Initiation into elderhood. Just as some people take their coffee black, I take my truths unvarnished. I was getting old, dammit. And there was nothing I could do to change it.

A sudden sadness descended, whispering don’t worry, it’s all downhill from here. I would have listened had it not been for one small detail. Thanks to membranous wings shaped like multi-jointed human hands, bats possessed exceptional maneuvering skills that exceeded those of their avian cousins. I thought of the chaotic grace with which they had moved under and around the bridge and into the trees. Maybe I was getting old. But age and experience had taught me flexibility, the art of pivoting around obstacles, adjusting to change. Catching sight of the lighted dock ahead, I breathed in the night air and breathed out the blue gloom that roosted in my mind. Whatever happened next, I’d manage. Just like the bats.