Wood is the material par excellence for the bird house, the only material which can be unreservedly recommended. Substitutes have been used with varying degrees of success or failure. What glass is for the window, wood is for the bird house. First, the birds are habituated to it. It is a good nonconductor of heat, it resists rain and extremes of temperature, and it can be made to harmonize with its setting. Over a long period of time it improves, rather than suffers, from exposure to the weather.
Soft wood with straight grain, such as pine or spruce, is preferable. It is easily worked, may be nailed with little danger of serious splitting, and is sufficiently durable. Slab wood, with or without the bark, and old fence-boards make the most generally effective bird houses. If new lumber is used, it should be rough, not planed; whether rough or planed, it should be treated with gray, olive, or dull brown stain of a medium shade. There are numbers of suitable oil stains on the market. The stain should permeate the grain of the wood, without actually coating it as paint does. Thickness of the boards should not be far from 1 inch. If slab wood is used, it may be anywhere from ⅜ inch at the edge, up to about 2 inches in the thickest part.
Leave the matter of materials for the nest itself entirely to the birds. Not only is it quite unnecessary to place twigs, straws, strings, or even choice feathers or other fluffy bits on or near the bird house, but such action tends actually to defeat its own purpose. The prospective tenants often seem to regard these well-meant efforts as evidence of a competitor who has the advantage of priority. This is especially apt to be the case when the materials are placed inside the house. Birds will sometimes steal nesting sites and even the raw materials of others but may choose to avoid the clash which such piracy entails, provided there are other sites and materials not too far to seek.
Entrance
There is always danger of the wood splitting when too large an auger hole is attempted. Before assembling the bird house, make an entrance in the front board. Start by drawing a circle the exact size of the doorway-to-be. Then, just inside this circle, bore four holes at equal intervals, using a bit not larger than ⅜ inch for the smaller entrances; not larger than ¾ inch for the larger entrances. It will now be not too difficult, by use of a keyhole saw or pocketknife and wood-rasp, to remove the wood still remaining inside the drawn circle. Placing the board horizontally in a vice will further insure against splitting while the holes are being bored.
Plate II. The Best and Most Simple Form of Artificial Nesting Site
With dimensions appropriate to the species, this is the most generally attractive type of house for all species excepting the Purple Martin. It is the type especially suited for the chickadee, nuthatch, and Tufted Titmouse.
1 THE BLOCK SAWED AROUND (TO DOTTED LINE) AND SPLIT IN TWO. 2 HOLLOWED OUT HOLES DRILLED FOR ENTRANCE AND FOR FASTENING PEGS. 3, 4, AND 5 SHOW THAT A NEST IS NOT DISTURBED BY OPENING HOUSE TO INSPECT. 6 THE “ARTIFICIAL WOODPECKER HOLE” IN PLACE. NOTE FASTENINGS FOR FRONT,—WOOD PEGS. 7 TOOLS FOR OBTAINING AND WORKING THE MATERIAL.