A Wood Duck hen, incubating within her nest box, checks out a nest-checker. Credit: Aaron Ward / Maryland Wood Duck Initiative via Cool Springs Press

Setting up bird houses is a great way to bring yourself a little closer to nature. Making small changes will help make your bird houses more beneficial to the birds you are hosting. The following is an excerpt from “Audubon Birdhouse Book, Revised and Updated: Building, Placing, and Maintaining Great Homes for Great Birds (New edition)” by Margaret Barker and Elissa Ruth Wolfson, on sale June 15, 2021, from Cool Springs Press.

An excellent first step toward building a great nest box or creating a reliable nesting structure for birds is to figure out what constitutes a poorly designed, ill-made one. Examples are all too easy to find at stores, garage sales and sometimes even at school and community birdhouse-building events.

A checklist of bad features — some of which may be eye -catching or even advertised as beneficial — mostly applies to nest boxes for smaller birds. It includes the following:

“Audubon Birdhouse Book, Revised and Updated: Building, Placing, and Maintaining Great Homes for Great Birds (New edition)” by Margaret Barker and Elissa Ruth Wolfson. Credit: Courtesy of Cool Springs Press

Heavily painted and lacquered nest boxes: Even though nontoxic, low-VOC paints are available, plenty of premade birdhouses on the market may contain toxic, including lead, paints. Another problem with brightly painted housing, especially dark colors, is that it can create oven-like conditions inside a nest box placed in the sun. Birds see color, but it is unclear what message colors may convey. In the wild, nesting sites are primarily brown tree holes and ledges, not highly colored miniature human houses.

Perches on nest boxes: Perches under entry holes allow predators, especially avian predators, to gain a foothold into the nest box and its contents. These are also used by House Sparrows to lay claim to nest boxes.

Generic-sized entry holes: Nest box entry holes should be designed to let certain birds in and keep other kinds of birds out. Entry holes that are too large may allow predators to come into the box. Entry holes that are too small could trap birds or damage their feathers. “Feather wear” occurs when birds make frequent trips into and out of nest boxes that have entry holes with tight fits, are rough or splintery. Entry holes should be appropriately sized, smooth and well-sanded.

Shoddy Construction: Nest boxes that are merely stapled together may be less expensive, but they will soon fall apart. Galvanized steel screws or exterior screws (i.e., “decking screws”) are the way to go.

This Eastern Screech-Owl and its Gehlbach-designed nest box both blend into their surroundings. Credit: Fred Gehlbach / Cool Springs Press

Incorrect floor Construction: Avoid removable floors, which can dump nest contents, and floors nailed flush to the sides, which allow rain into the seams. Nonremovable, one-quarter-inch minimum recessed floors are recommended.

Nest Boxes made from Paper Milk Cartons, Plastic milk Jugs, Corrugated Cardboard or Coffee Cans: The idea of recycling materials for nest boxes sounds like a good one. But many of these materials, sometimes used to make nest boxes with children, are flimsy, not insulated, easy targets for prey and quickly saturated by rain or, in the case of plastic jugs and coffee cans, prone to overheating. They do not provide “optimum” safe shelter for birds, especially featherless chicks that can become wet and chilled and die of hypothermia.

Nest Boxes for Warblers and Goldfinches: Although the male American Goldfinch and bright, good-looking warblers do make for colorful advertising, these birds are not cavity nesters and do not use nest boxes. Steer clear of nest boxes “designed” for them. Often the most bedazzling birdhouses for sale are the most dangerous for birds. Especially hazardous may be artistically crafted birdhouses that resemble miniature human homes. Buying a birdhouse as a work of art is fine. But enjoy this object inside your home. Do not put it outside for wild birds.

These rustic bird homes could do birds more harm than good. The “porch perches” invite predators. The roof construction invites rain. they are stapled together. Credit: Stock Photo / Cool Springs Press

Setting Up and Settling In

A well-built nest box won’t do the intended bird residents any good if it is improperly placed. In fact, it could do them harm. A good rule to follow is to locate nest boxes so that food, water, and shelter are nearby. Tom Comfort of the North American Bluebird Society says, “Remember that food is a bird’s first criteria. They nest near their source of food.” But different species have different food and habitat needs, and it is important for the health and safety of the birds to know what those are. For example, Purple Martins need a ready supply of flying insects; Wood Ducks require a nearby body of water; Burrowing Owls depend on premade tunnels for their nesting burrows.

Improperly placed under tree branches, this Wood Duck nest box became an invitation to squirrels, not ducks. Credit: Aaron Ward / Maryland Wood Duck Initiative via Cool Springs Press

Care should be taken to observe sun and shade during certain times of the day and locate nest boxes appropriately. Note which direction bad weather arrives from, then make sure nest box entry holes are not aimed that way. Keep nest boxes away from overhanging trees and places that give pests and predators — including squirrels that prey on bird eggs — easy access to the nest site. Mount nest boxes at levels where they can easily and regularly be checked. Mounting methods are discussed later in this chapter.

Nest boxes and nesting sites for certain birds may not be complete without adding nesting materials such as white pine wood chips (found in pet stores as small animal bedding) to nest boxes or adding nesting sticks to platforms. Other birds may appreciate bowls of pine needles or feathers with which to line their nests. Muddy sites close by are welcomed by several bird species, including Barn Swallows. Find out which species require which materials to help them settle in.

This excerpt has been edited for clarity and length.