Building an attractive, sturdy and weather-proof birdhouse is very easy to build. Wood is a particularly good building material because it breathes, is durable and has good insulating qualities. The ideal choices are naturally decay-resistant wood such as cedar, redwood or a good grade of exterior plywood. It should be at least ¾” thick as anything less will result to heat built-up which is very harmful to young birds. It doesn’t really matter whether the wood is slab, rough-cut or finished as long as the inside has not been treated with stains or preservatives. Fumes from chemicals are likewise harmful to the birds.
Cypress and cedar wood would require no painting but pine and plywood houses will last longer when coated with water-based exterior latex paint. Brown or dark-green stain applied only to the exterior will camouflage the house and prevent rough boards from rotting. Purple Martin houses are usually white while tan, gray or dull-green works bests for the other cavity nesting species. These colors will reflect heat and are less conspicuous to predators.
Never use lead-based paints if there is a need to paint or varnish to preserve the wood. It is possible that birds may peck at the painted wood and ingest the toxic paint in the process. One good option is the use of natural oil on the outside of the house such as linseed oil that is food safe and not petroleum-based for maximum safety. The inside of the house is best left as natural wood only.
Brightly painted birdhouses are fun to see but draw unwanted attention to themselves. It helps to keep the backyard bird families safe when the birdhouse blends into its surroundings. Bird enthusiasts can compensate through the use of garden ornaments, stepping stones or flowers.
Gluing all the joints before nailing them will extend the life of the birdhouses regardless of the kind of wood used. Galvanized or brass shank nails, hinges and screws are more rust resistant and are able to hold boxes together more tightly as they age. Hinges and fasteners can both be functional and decorative but extreme care should be taken so that there will be no sharp edges that can harm the birds.
Birdhouses should never be made of metal since the hot summer sun heats metal to very high temperatures that can kill nesting birds. Reflective metal also attracts predators. Purple Martins have their own special aluminum birdhouses. Other possible materials are properly designed pottery, concrete and plastic. Concrete offers one unique protection as squirrels cannot chew their way in. Natural gourds make very attractive birdhouses as well.
Some experts recommend using rough sawn wood to make it easier for birds to grip with their feet. It can be very difficult for some species to get out of the house if the inside surface is too smooth. Cutting grooves on the inside front panel of the house or adding a small strip of hardware cloth on the inside under the entrance to serve as an escape ladder for the birds will make the box more bird-friendly.
Provision for nest building materials is not necessary for box occupants. However, materials such as yarn, paper, feathers and pieces of string may be placed near the birdhouse. Birdhouses that do not use nesting materials such as those for flickers and woodpeckers should have its floor covered with a layer of sawdust or ground cork.