Homeowners can make their backyards attractive to bats in a number of ways, says Jim Kennedy, habitat protection coordinator for Bat Conservation International, an Austin-based nonprofit.

"It's not rocket science. We look at what animals are needing and make things as friendly as possible," he says. "Leaving your place in as natural a state as possible is good for all wildlife."

For bats, that includes:

• Leaving hollow or dead trees in the landscape as long as they don't pose a hazard. They are good food sources for insects and shelter for bats and other wildlife.

• Avoiding pesticides. Trace amounts of pesticides in insects can bioaccumulate, and those levels can build up in the fatty tissues of bats, Kennedy explains.

• Creating a diverse landscape. A mowed lawn won't have a rich supply of food for insects. Having more insects means more of a chance bats will have something to eat year-round.

• Maintaining a water source. Bats swoop to drink, so they need an open area and a relatively large pool of water, such as a stream or pond. They will drink from swimming pools, but chlorine is not good for them.

• Putting up bat houses. Anybody who has some property, even a city lot, should put up at least one bat house, Kennedy says. BCI's website, www.batcon.org, provides building and installation instructions, along with a list of places to purchase certified bat houses. Some retailers sell structures that are too small for the bats.

Reggie Regan, owner of Lone Star Woodcraft in Garden Ridge, builds bat houses certified by BCI. His three models of houses range from $99 to $280 and accommodate 100 to 700 bats.

The houses, which look like wall-mounted mailboxes, are made of rough-cut western red cedar to give the animals a surface they can hang on to. They are divided into 3/4-inch chambers, where the bats huddle.

If you're thinking about installing a bat house, consider these tips:

1Place on the sunny side of the house where it gets six to eight hours of sunlight a day. The creatures like warm temperatures, so the top of the box should be painted a dark color to absorb sunlight.

1Bats need room to swoop in and drop out of the house, so place the house at least 12 feet off the ground.

1Keep at least 20 feet from branches that could shade the house or hinder the bats' path.

1Bat droppings can be pungent. Don't place the house above a window or anywhere the odor will become a problem.