Nest Box Design Basics—Materials
Look through any book or catalog and you'll see bird houses of all sizes and shapes, with
perches and without, made of materials you might not have thought of: recycled paper,
gourds, plastic, rubber, pottery, metal, and concrete.
Of all the available building materials, wood is about as good as you can get. It's durable, has good insulating qualities, and it breathes. Three-quarter-inch-thick bald-cypress and red cedar are recommended. Pine and exterior grade plywood will do, but they're not as durable.
It makes no difference whether the wood is slab, rough-cut or finished, as long as the inside has not been treated with stains or preservatives. Fumes from the chemicals could harm the birds.
There's no need to paint cypress and cedar, but pine and plywood houses will last longer with a coat of water-based exterior latex paint. White is the color for purple martin houses. Tan, gray, or dull green works best for the other cavity nesting species. The dull, light colors reflect heat and are less conspicuous to predators. Don't paint the inside of the box or the entrance hole.
Regardless of which wood you select, gluing all the joints before you nail them will extend the life of your bird house. Galvanized or brass shank nails, hinges, and screws resist rusting and hold boxes together more tightly as they age.
Resist the temptation to put a metal roof on your bird house. Reflective metal makes sense for martin houses up on a sixteen-foot pole, but when it's tacked onto a roof of a wood chickadee house, the metal is more likely to attract predators.
Natural gourds make very attractive bird houses. They "breathe," and because they sway in the wind are less likely to be taken over by house sparrows and starlings.
Grow your own gourds and you'll have dozens to choose from in the years ahead. If you don't have the space to grow them, a coat of polyurethane or exterior latex (on the outside only) will add years to the one you have.
Properly designed pottery, aluminum (for purple martins only), concrete, and plastic houses will breathe and are durable, but don't drop them.
Be sure to provide ventilation, drainage, and easy access for maintenance and monitoring. Concrete (actually a mix of concrete and sawdust) offers protection other houses cannot: squirrels cannot chew their way in.
This article was written by the DEPARTMENT OF THE INTERIOR U.S. FISH AND WILDLIFE SERVICE
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