A group of workers were preparing a home in Menlo Park for power-washing when they discovered a colony of 83 nesting bats on Wednesday.

The Mexican free-tailed bats were tucked behind a mural of St. Francis of Assisi (the patron saint of animals) that the team removed from the side of the house.

"When the bats started to fall to the ground, the workers called us for assistance," Buffy Martin Tarbox, a spokesperson for the Peninsula Humane Society said in a statement. "Our staff quickly arrived and were concerned the bats may have been injured so we carefully scooped them up and brought them to our wildlife center for evaluation."

Humane Society and SPCA staff carefully provided the bats with oxygen and placed them in incubators to help with circulation and increase their body temperature, before transporting the creatures to the wildlife care center for evaluation.

"The bats responded well to the oxygen and heat treatment and were released back to the wild yesterday at dusk," according to Tarbox. "This is the highest number of bats we have ever received at one time in our Wildlife Care Center. On average we receive one bat a month, so 83 bats were quite unusual for us."

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Mexican free-tailed bats are medium in size (3.5 inches in length on average) and native to the Americas. They feed mainly on moths including the larvae that eats farmers' crops.

They are considered a species of special concern in California as their population is declining due to the destruction of their habitat and pesticide poisoning.