squirrels, bees, wasps and other
small animals may take up residence in bird houses. If not acceptable, remove the nests.
Otherwise, you will probably need to put up additional houses to accommodate both the
unexpected tenants and the desired ones. General Instructions for Houses and Platforms
Birds and mammals need different kinds of houses or platforms in different habitats. These general instructions will help you build and place houses and platforms for the most popular occupants of wildlife homes in Pennsylvania.
These general instructions apply to all plans:
1. Select a box for a specific bird or mammal. Different species have different house-size and entrance-hole requirements.
2. Provide a hinged side or roof so the house can be easily checked and cleaned each year. Hinges should be rustproof. Duck and owl box roofs fastened with a hook and eye can be opened by raccoons. It is much better to use several paired roofing nails with large heads. One nail from each pair goes on the side of the roof, the other on the upper edge of the side. Wire these paired nails together.
3. At least four 1/4-inch diameter drain holes should be drilled in the bottom of every house, except the Peterson bluebird house. The sloping floor and space that allows the swing-door front to open provide for drainage on that house.
4. Don't put perches on any bird house. Only house sparrows and European starlings prefer perches. If you have a house with a perch, remove the perch. A slab of wood with the bark attached may be placed horizontally under the entrance hole of a wood duck or common merganser box to make it easier for landing at the entrance.
5. The top-front edge of a bird house should overhang at least two inches to help protect the entrance hole from wind-driven rain and to keep cats from reaching in from above.
6. At least two 1/4-inch holes should be drilled near the top of the right and left sides of all bird houses - except duck boxes and winter roost boxes — to provide ventilation. Providing adequate ventilation is especially important for small bird houses.
7. Use galvanized nails to build houses if necessary, but remember that they loosen up as wood expands and contracts in Pennsylvania's extreme weather conditions. Cedar and redwood nest boxes probably should be made with concrete coated or ring shank nails. They won't allow the boards to loosen up.
8. The sides of a bird house should enclose the floorboard; don't nail them to the top of the floorboard. The arrangement prevents rain from seeping between sides and floor and then into the nest. Recess the floorboard 1/4 inch up from the bottom of the sides to help prevent deterioration caused by moisture.
9. Do not use tin cans, milk cartons or metal as nest box materials. Metals heat up in direct sun, overheat the eggs, and kill the young. However, commercial martin houses made from aluminum are acceptable. Commercial plastic wood duck houses are also acceptable, but should be placed in shady locations.
10. Wood is the best material for houses. Three-quarter-inch boards are the easiest to work with. Softwood such as pine is fine for smaller nests, but cedar, redwood or cypress should be used for larger boxes. Pine or plywood can be used for duck boxes providing the outside of the box is treated with wood preservative. Do NOT use pentachlorophenol (penta) or wood treated with green preservative. The green copper-based preservative, when exposed to water, can produce poisonous vapors. A well-constructed house should last 10 to 15 years. Large boxes such as duck boxes can be painted with wood preservative on the outside to extend their usefulness. The back should be coated several times because it is most prone to rotting. Do not paint, stain, or treat a box with creosote.
11. Exterior finishes are a matter of personal preference. In fact unfinished structures made of redwood, pine, spruce or exterior plywood will turn gray and last for years. If you want a colored structure, semi-transparent oil-base stains are best. They will penetrate the wood. A single application will last three years on a smooth surface, longer on a rough one. Select a stain that does not contain pentachlorophenol preservative.
12. Purple martins, mergansers and wood ducks do not defend territories around their nests. Therefore, martins should be provided with "apartment type" houses. Duck and merganser boxes can be clustered in groups of two or four. Houses for other bird species should be spaced far enough apart to reduce territorial conflicts. Bluebird houses need 100-yard spacing.
13. Mice, squirrels, bees, wasps and other
small animals may take up residence in bird houses. If not acceptable, remove the nests.
Otherwise, you will probably need to put up additional houses to accommodate both the
unexpected tenants and the desired ones.
14. If wasps take over a house, remove the wasp nest and spray the interior with a disinfectant such as Lysol. Use extreme caution to avoid being stung. A can of aerosol insecticide may be necessary during this process for "self-defense." If an ant colony becomes established, place Terro or some other commercial ant killer in an upside down pop bottle cap under the nest.
15. Blowfly eggs and larvae may be found in a bluebird nest. The larvae will suck blood from the young birds. If these are found, lift up the nest with your fingers and gently tap the nest. The larvae will fall through the nest and can be removed from the bottom of the box.
16. When house sparrows and European starlings are not welcome, repeated removal of their nests (six times, or so) will generally discourage further attempts. House sparrow nests are typically characterized as messy structures of grass, assorted litter, and garbage. Starling nests are an untidy structure of stems and leaves.
17. When the nesting season is over, open the house and leave it open throughout the winter to prevent deer mice from using it. Otherwise, these mice may defend their box from returning songbirds in the spring. They may even kill and eat birds which enter their box.
18. Be sure to allow for the width of the saw blade when marking a board.
19. Remember that the width and depth of lumber purchased at lumber yards is smaller than its standard description. For example, a I" x 6" board is actually 3/4" by 5 1/2". A 2" x 4" is actually 1 1/2" x 3 1/2". The plans in this booklet utilize the actual dimensions of boards to make the most efficient use of wood.
20. Sawdust may not be the best material for lining nest boxes for birds of prey or waterfowl (northern screech owl, barred owl, northern saw-whet owl, barn owl, American kestrel, wood duck, hooded merganser, common goldeneye, and common merganser). It tends to pack down when wet, and retains moisture. Wood chips from a chain saw seem to be a better lining; or place a 1/2" layer of pine needles on the box floor. They allow for better drainage and less water retention.
21. Any birdhouse entrance hole 13/8 inches in diameter or larger will admit house sparrows and any entrance hole larger than 1 1/2 inches in diameter will admit European starlings. Wherever possible, the entrance hole dimensions for songbirds in this booklet are designed to exclude these pest species.
22. Try to place boxes in "best" (for each species) habitats where there is a shortage of acceptable natural cavities.
23. If a box must be attached to a live tree, use aluminum nails, or the tree fastening techniques illustrated in (Plan 26).
24. Screen should be placed inside the entrance of all boxes large enough for a wood duck to nest in. This provides a way for the ducklings to get out. Any boxes with the diameter of 2 9/16" opening or larger should have screen inside the entrance.