They arrive in Augusta each spring -- just before the golf fans -- and linger until late November.

While they're here, the migrating bats raise their young and consume millions of insects during nightly feeding forays that take them hundreds of miles.

They also need someplace to stay, but freeloading bats aren't always welcome neighbors.

"Sometimes people complain about the noise, or the odor," said Lee Kennamer, a wildlife biologist with Trutech Inc., a nuisance wildlife service based in Marietta, Ga.

Mr. Kennamer and his crew are spending a week in Augusta trying to evict colonies of Mexican free-tailed bats that have taken up residence in more than a dozen apartment buildings off Washington Road.

The largest known colony of Mexican free-tailed bats is in Texas, near San Antonio, where 20 million bats consume 200 tons of insects every night.

The colony in Augusta is smaller: anywhere from several dozen to several thousand -- or even tens of thousands, he said.

Although bats are protected as nongame animals, they are also plagued by habitat loss and are easily harmed by pollution.

Mr. Kennamer's objective isn't to harm the bats. He just gets them to move.

"You find their entry points and block them," he said, pointing out tiny openings near a building's roofline where bats enter.

Such openings can be fitted with "bat valves" that serve as one-way doors that allow the creatures to leave but not re-enter.

"If they can't use their usual entry point, though, they'll look for other ways to get in," he said. "So we have to go around to all the buildings and seal up areas they might try to use to move into."

Large bat colonies typically require large food sources. Washington Road isn't a bountiful hunting ground, but the nearby open expanses of Augusta National Golf Club, Augusta Country Club, Lake Olmstead, Augusta Canal and the Savannah River might play a role in the bats' choice of roosts.

"They like ponds, pastures with flat surfaces -- any open area where they can find food," he said. "It's not unusual to find houses overlooking golf courses that have bats living inside."

Although they are gentle, abiding little creatures, bats are also noisy and can generate huge quantities of nitrogen-rich droppings, known as guano.

"Usually, this species likes to live in caves," Mr. Kennamer said. "But in places without caves, they will move into barns, houses, anything that gives them shelter."

Were it not for the abundance of manmade structures, the species might not be as stable as it is, he said.

Typically, the Mexican free-tails stay in Augusta until November, when they leave for warmer locales far to the south.

"When they're traveling, some groups are so large they show up on Doppler radar," he said.