Creating shelter for birds on your property
FORESTS ONCE fashioned a broad range of habitats and homes for wildlife. As trees matured dead branches broke off, creating holes in live tree trunks. Birds, mammals, and even reptiles found shelter or nesting opportunities in such cavities. Woodpeckers, chickadees and nuthatches excavated additional holes that other wildlife could later adopt on a seasonal basis.
However woodlands now rarely grow old—they have been profoundly altered by pulp companies and processors, and nesting holes in trees are scarce. Whether your property is small or large, by placing nest boxes in young forests near water or around a home, you can accommodate and attract more wildlife. A good time to place the boxes is during late winter to early spring, before nesting seasons begin.
Do not use pressure-treated wood with chemical preservatives or paints that might prove toxic. Nest boxes should remain untreated and unpainted inside. The wall with the entrance hole should be rough or grooved inside, so fledglings can climb to freedom. (See “DIY Best Practices,” page 24, for more tips and insights.)
The illustrated nest box on the following pages is simple to build. Overall minimum interior sizes, hole diameters and suggested locations for placing the box depend on the species—it’s important to learn about the birds you want to attract, and where they nest. The following chart lists preferences for box height above ground, landscapes and sizes of territories, but there’s more to consider. For example, tree swallows search for open areas near water. Chickadees like to nest near shrubs and bushes. Flickers adopt a nest box more readily if it is placed above foliage. Purple martins are usually housed in birdhouse condos, which should be located within the area they frequent.
Wood ducks, goldeneyes, hooded and common mergansers prefer a nest box near—or standing in—water. More specialized designs exist for many species, including waterfowl, bluebirds, owls and purple martins.
Deterring unwanted guests
Your new bird house may attract starlings and to a lesser extent, house sparrows. Let them have it, or cover the entrance temporarily until migratory birds arrive in your area.
Red squirrels and flying squirrels may quickly adopt your box. A young raccoon took over our barred owl nest box one year. It eventually grew too fat to get in.
If you place the box on a tree, consider clearing adjacent limbs from nearby trees to limit wildlife tree-to-tree travel. Place a section of metal stove pipe some distance up around the trunk of the nest tree to deter animals jumping up from the ground. (Affix the pipe so the tree trunk can still expand as it grows.) If you are using a pole, consider smooth metal that is difficult to climb.
Posts can also be outfitted with rain downspout sections; inverted cones or guards can be installed on trees, posts or poles to avert climbers.
Remember to clean the debris out from inside the nest box after the breeding season—this helps to minimize parasites like lice that overwinter in the box to “welcome” next year’s nestlings. When reaching into a nest box, be careful of wild bees, squirrels, and wasps that may have taken up residence.
I purchased young forest land four decades ago, which needed short-term help to become more wildlife-friendly. Building and erecting nest boxes was one way to help. Our property now has lots of trees with holes, and the old nest boxes, usually without bottoms, now serve the bats. One nest box is maintained for our fascinating barred owl neighbours. I installed the box in the woods long ago, by the brook where they were hooting late one winter. They’ve been raising owlets there ever since.
For more information, Bob Bancroft recommends Building Bird Houses for North American Birds, by John Plewes (Veritas).
DIY best practices
- Once you’ve determined the size of the entrance hole for the kind of birds you want to attract, place the top of this hole about 11/4 inches down from the underside of the roof.
- Don’t place a perch outside the nest entrance. It can assist predators in an attack, and often impedes the swooping upward flight path of birds returning to the box.
- If you are using lumber of varied thicknesses, remember that the minimum inside dimensions are most important to the birds.
- There should be no protrusions (nails, screws) inside the box that might cause injury.
- Drill holes in the floor to allow water to drain out.
- If you wish, drill a few small holes on the sides near the top of the box, below the roof overhang. This provides ventilation during hot spells. However in Atlantic Canada birds often suffer cold spells in the spring, so ventilation may be unnecessary.
- The top or one side of the box should open for annual cleaning of old nest material. Pre-drill holes in the closed position, then press in nails that can be pulled out later with your fingers for house cleaning.
- A groove made across the underside of the roof overhang on the front and sides will act as a rain drip.
- Most birds bring their own nest material. Exceptions are woodpeckers, flickers, owls and ducks, which prefer a layer of wood chips, dry, rotted wood or shavings—not sawdust—to a depth of 1-3 inches in the bottom of the box.
Nest boxes can be attached to trees, poles, posts or to the side of a house. Here are a few suggestions. Note: the entrance hole should face away from storm winds that prevail during the breeding season—north-facing is usually a good option.
- Extend the back wall above and below the box itself—then it can be nailed (or drilled and screwed) above and below.
- Attach a longer piece of wood to the outside of the back wall and follow above.
- Hang the box on a tree trunk or from a limb with hooks screwed into the sides of the box and the tree or post.
- Wire from nails or screws in the box to nails or screws in the tree. Refrain from wrapping wire entirely around a tree to prevent injury to it.