There are a number of ways to attract songbirds to our landscapes. The best way is to plant trees, shrubs, perennials, and annuals that produce food and cover for the birds.

Bird feeders and bird baths will also attract birds, especially if there are plenty of plants already in the landscape. A relatively small number of bird species nest in hollow trees. Hollow trees are pretty rare in an intensely managed landscape, but nest boxes will sometimes fill the gap and attract hole nesting birds.

Some of the species that will nest in birdhouses are purple martins, wrens, chickadees and titmice. English sparrows and starlings also nest in houses, but because of the competition they provide for less common native bird species, we do not usually encourage them to use our bird houses.

In terms of basic rules, if you want to be successful with birdhouses consider that each species has specific preferences for birdhouse size, hole diameter, and placement height. It rarely works just to build a house as a decorative item without any thought to bird requirements.

Hundreds of good resources are available with plans for building and caring for birdhouses. Every library and bookstore has books with birdhouse plans and the internet has many good sites. In addition to building birdhouses, they can be purchased at bird supply stores, plant nurseries, feed stores, pet stores and on the Internet.

Now is the time to put birdhouses up, so that they have an opportunity to weather and also be noticed by the birds seeking a nest site. Purchase houses that can be cleaned each year.

Purple martins are the bird species most identified with bird houses. They originally nested in hollow trees, but now rarely do. They rely almost entirely on human made colonial houses with eight to 12 boxes that are mounted on poles 15 to 20 feet in the air.

The martins feed on flying insects, so are attracted to houses that are surrounded by open areas where they can swoop to and fro to catch insects. A martin house placed in the middle of the woods rarely attracts any martins.

The scouts arrive sometime in February and nesting is completed before the end of July. Martin nest boxes are built to provide about 6-by-6-by-6-inch interior space with a 2.5-inch entrance hole.

A major problem in providing nesting sites for martins is competition from English sparrows and starlings. Some landlords raise and lower the houses often in the process to remove the unwanted nests. Most of us, however, wait until about Feb. 15, to raise the house (sooner, if martin scouts appear) and rely on the martins to get access to at least some of the nest boxes.

Our nesting wrens require houses with dimensions of about 4-by-4-by-8 inches. The entrance hole should be 1.5 inches in diameter. Place Bewick and Carolina wren houses on a pole or fence at about six to eight feet from the ground.

Like house wrens, we sometime see bluebirds passing through San Antonio, but they do not seem to nest in the city. Bluebird houses are available everywhere. They are about the right size for the wrens, titmice and chickadees.

Carolina chickadees and tufted titmouse are also relatively easy to attract to a nesting box placed in our landscape. They will use the same size house as the wrens, but seem more comfortable when it is placed on a tree trunk to about eight to 15 feet high.

Calvin R. Finch, Ph.D., is a horticulturist and the director of water resources for the San Antonio Water System.