Rooms to Let, Cheep, Cheep

Because many birds are busy shopping for their spring nesting sites, winter is the perfect time to put up birdhouses around your property

02-01-2008 // Cynthia Berger
Female wood duck by George R. Parker

I THOUGHT I'd hate being a landlord. But my tenants are great: They're pleasant to have around, they have strong family values and I like their music. Now I'm even thinking of acquiring more units. You see, my "rental" is a wooden birdhouse, mounted on a pole at the back of my yard, and the tenants that move in each spring are a pair of Carolina wrens.

If you'd like to try your hand at being a bird landlord, this is a good time to get in the game. Right now—in the middle of winter—is a perfect period to put up backyard birdhouses, because the cold months are actually when many species that use these accommodations are shopping for their seasonal homes.

"It depends what species you are trying to attract," says Kaycee Lichliter of Middletown, Virginia, an experienced birder who collects data about her backyard tenants for the Birdhouse Network, a citizen science project of the Cornell Lab of Ornithology. "Around here, eastern bluebirds get serious about looking for a nest site in February and March because they lay their first eggs in April."

"A lot of birds start prospecting as early as January or February in the mid-Atlantic region where I live," adds NWF Chief Naturalist Craig Tufts. "We tell people to have boxes up no later than March 1."

Don't expect every bird you see in your backyard to be attracted by your offer of a cozy room. "People are always calling me to ask, 'How do I get the redbird to go in the box?'" says Keith Kridler, another Cornell volunteer and expert on birdhouse design who lives in Mt. Pleasant, Texas. "Not going to happen!" Redbirds (a.k.a. northern cardinals) simply don't care for the confines of a birdhouse—they build their open-cup nests in the concealment of a conifer or shrub. Other backyard favorites including goldfinches, jays and orioles also eschew birdhouses.

A few of the common backyard birds that scorn an actual house will enjoy a structure called a "nest shelf," notes Tufts. Robins, phoebes and house finches are among the species that like to construct their nests on a flat ledge. (Nest shelves, and plans for building your own, are available from the same sources that supply birdhouses.)

The birds that use houses for nesting and rearing their young are those that also seek out natural cavities in trees. Some 85 species nest in cavities in North America; about three dozen of those will nest in birdhouses. The most common backyard denizens to use houses include various species of chickadees, titmice, bluebirds and wrens. But you could attract other species depending on what kind of habitat you have in or near your yard—and the kind of box you put up.

"I have four boxes at my house," says Lichliter, who lives in an area bordered by woods and farmland, "and I usually attract both eastern bluebirds [which tend to like mowed grassy fields] and house wrens [which like yards with small trees and shrubs]. And last year, I had a nest of tree swallows [often found near water]." Lichliter also put up a screech-owl box (a large box with a good-sized entry hole) high in a pine tree in her yard. A screech-owl moved in a week later.

In addition to supplying nesting habitat, National Wildlife Field Editor George H. Harrison, author of more than a dozen books on birds and backyard wildlife, sees another benefit to putting up boxes: "The best part of renting birdhouses in my backyard," he says, "is the fascinating insight I get into the secret lives of birds, from nest building to the solo flights of babies from the houses." Harrison has watched everything from black-capped chickadees and screech-owls to wood ducks and northern flickers nesting at the same time in boxes on his Wisconsin property. "To fill your birdhouses, you simply need to meet the requirements of the renters," he says.

Needless to say, the size of the entrance hole limits which species can enter—and which pest species such as starlings cannot—and the floor plan must accommodate the species' nest. Chickadees and titmice, for example, "nest in dense natural habitat, such as stands of small trees," notes Harrison. To attract these birds, he says, put up birdhouses that have 1 ¼-inch diameter holes, centered 6 inches above the bottom of the nesting floors, in small tree thickets. (To read about the nest box requirements of other birds, see "Birdhouses for Rent" below.)

These days shopping for a birdhouse can seem like a major real estate investment—prefab houses have a lot of features and some come with a hefty price tag. If you're the do-it-yourself type, it's easy to build a birdhouse. Either way, you want to be sure you're choosing a box that will help, not harm, your tenants. Desirable features may include thick walls constructed of untreated wood for insulation, holes for ventilation and drainage, and an extended and sloped roof to keep out the rain. You wouldn't buy or rent without insurance, and your birdhouse needs some too—in the form of a baffle to keep out raccoons, snakes, house cats and other predators that steal eggs and chicks. "If you put a birdhouse up on a pole without a guard you are basically serving lunch," says Lichliter. One of the best baffles, according to Kridler, is made from a length of stovepipe.

By renting out a little backyard real estate to feathered tenants, you'll not only have the pleasure of watching their offspring fledge, you'll also be providing a much needed resource for birds, some of which also use birdhouses for winter roosting. Our urban and suburban propensity for creating tidy landscapes means natural nesting cavities are in short supply in many areas. "We encourage people to provide places where wildlife can raise their young," says Tufts. "It's one of the best things you can add to your landscape."

Pennsylvania writer Cynthia Berger's article about gray jays and global warming also appears in this issue.


Birdhouses for Rent

By George H. Harrison, Field Editor and Backyard Birding Expert

In order to maximize the number of bird tenants in a backyard habitat, certain nest box and habitat requirements for each species need to be met. Landlords, take notice:

Wood Duck
One of the few cavity-nesting ducks, wood ducks (female, above) naturally nest in a tree cavities, but will readily inhabit a house. Requirements: 10" x 10" x 24" high; hole: 4" wide x 3" high (elliptical), centered 20" above the floor; color: earth tone; placement: on a post 3–5' feet above open water or on a tree 12–40' high near water; nesting material: 3–4" of wood shavings on the floor of the house. Habitat: These tree ducks look for houses that are in trees on or near lakes, rivers or streams, to which they can lead their broods after the ducklings vacate the house.

Wren 
House wrens and Carolina wrens are among the easiest birds to attract to birdhouses. Requirements: 4" x 4" or 4" x 6" base, 8" high; hole: 1-1/8", centered 6" above the floor; color: earth tone; placement: 5–10' high on post or hanging in a tree. Habitat: House wrens prefer their houses hanging from a small tree in the middle of a yard, or along the border of an open yard. Carolina wrens will go into a birdhouse that is well hidden in natural habitat (near trees or tall shrubs).

Bluebird
All three bluebird species (eastern, western and mountain) will use birdhouses. Requirements:5-1/2" x 5-1/2" x 10" high; hole: 1-1/2", centered 6" above the floor; color: earth tone; placement: 5–10' on post facing open field (preferring east, north, south, and then west facing directions). Habitat: Bluebirds feed their young insects they capture in open, grassy fields. Their houses are most acceptable if placed on a post that faces, or is very near, an open field where they can find food.

Chickadee and Titmouse
All species of chickadees and titmice will use birdhouses. Requirements: 4" x 4" or 5" x 5" base x 8" high; hole: 1-1/4", centered 6" above the floor; color: earth tone; placement: 4–8' high in small tree thicket. Habitat: These birds nest in dense natural habitat, such as thickets or stands of small trees.

Tree Swallow
A tree swallow will occupy a house of the same dimensions, location and color as a bluebird house, but should be near water. Habitat: Like bluebirds, tree swallows like to catch their insect food above open fields or water. Their houses should be placed facing this kind of natural habitat.

Purple Martin 
Purple martins will rent apartment houses that will accommodate numerous families. Requirements: multiple apartments 6" x 6" x 6" each; 2-1/2" hole, 2-1/4" above floor; color: white; placement: 15–20' high in the open, near water. Habitat: Long sweep of grassy lawn or field should surround the martin apartment house as these birds hunt insects on the wing. A nearby utility wire may make the habitat even more attractive, because purple martins like to perch on or near their apartment houses.

Screech-Owl
Screech-owls are more common in backyards than most people realize, because they are nocturnal. They will nest in summer or roost in winter in a birdhouse of the same dimensions and placement as that of a wood duck house. Roosting owls will sit in entrance hole at dusk. Habitat: Birdhouses mounted on the trunk of a tree in a woodland of mature trees will bring owl occupancy either for nesting in early spring or for roosting in winter.

American Robin
Because they often nest on ledges and downspouts on people's houses, American robins may also use a shelter that is a three-sided birdhouse. Requirements: 6" x 6" x 8" high, open front; color: earth tone; placement: on side of building, arbor or tree. Phoebes and barn swallows will utilize this kind of shelter if placed under a deck for the phoebe, or in a barn for the swallow. Habitat: The shelter should be mounted in a location surrounded by natural habitat, including mature trees and grassy lawns for hunting earthworms.

Woodpeckers
All woodpeckers nest in tree cavities, but northern flickers, red-headed woodpeckers and downy woodpeckers may also take up residence in houses of varying sizes. Northern flicker requirements: 7" x 7" x 18" high; hole: 2-1/2", centered 14" above the floor; color: natural; placement: 8–20' high on tree trunk; nesting material: 4" of wood shavings on floor. Red-headed woodpecker requirements: 6" x 6" x 15" high; hole: 2", centered 6–8" above the floor; placement: 8–20' high on tree trunk; nesting material: 4" of wood shavings on floor. Downy woodpecker requirements: 4" x 4" x 10" high; hole: 1-1/4", centered 6–8" above the floor; placement: 8–20' high on tree trunk; nesting material: 4" of wood shavings on floor. Habitat: Because woodpeckers are woodland birds, they will be more likely to occupy birdhouses that are mounted on the trunks of mature trees in the middle of woodlands.

Birdhouses can be crafted in a workshop, or they can be purchased at a local bird supply store.

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