Yolo Causeway home to 250,000 bats this time of year, swarming sky in "ribbons" at sunset

YOLO COUNTY -- This time of year, more than 250,000 bats make their home under the Yolo Causeway.

It's quite a sight to see when the colony, mostly made up of pregnant or nursing females, heads out for dinner each night.

"I call it a ribbon when they come out. Some people call it a cloud," said Corky Quirk, program coordinator for the Yolo Basin Foundation.

Watching and waiting for the show Friday night was a sold-out Bat Talk and Tour , a group of about 70 people eager to see the bats take flight.

Each night around sunset, the bats can be seen filling the sky by the thousands. It's like ringing the bat dinner bell at the bug buffet.

"It's beautiful and amazing. I love nature," said one woman on the tour.

Quirk's mission at the Yolo Basin Foundation has been to change how people perceive these tiny creatures.

"I think a lot of the reason we fear nocturnal animals is because we often don't have an opportunity to learn about them," said Quirk.

The foundation hosts about 4,000 people on its tours each summer that start with a quick lesson in the classroom about bats, even allowing people to meet a bat up close.

"Once they meet the bat, the live ambassador bat, I see minds change," said Quirk. "Bats are incredibly important and not dangerous."

The causeway is primarily home to the Mexican free-tailed bat. The migratory colony is the largest in the state of California.

Bats nationwide save farmers billions of dollars every year by eating bugs that damage crops. They even feast on pesky bugs like mosquitoes.

"So these guys are super helpful," said Quirk.

But why are they tucked under the causeway and not in a cave or a tree? Quirk says, first, human development has led to a loss of habitat over the years, but the climate of the causeway is very attractive to the bats.

"The temperature is good, the black asphalt absorbs the heat, the cement holds the heat stable. Those crevices are pretty darn deep, so there are almost no predators," said Quirk.

The next time your evening commute takes you by the bypass at sunset, watch the sky for the critters creeping out just above.

The Bat Talk and Tour runs weekly through September. Tickets are just $15 for adults and $5 for kids ages 6-17. Children under 5 years old can attend for free.