Ken Bevis, Stewardship Wildlife Biologist, Washington Department of Natural Resources, ken.bevis@dnr.wa.gov
Everybody wants to help wildlife, right? But how do we do that?
Well, start with their three big needs; food, water and cover. If all are adequately provided in the local habitat, (with enough space for home ranges and territories, of course), voila! Wildlife populations.
But sometimes something is missing, or in scant supply. These become limiting factors, and populations may be reduced or even absent. Habitat enhancements can either provide the missing pieces, or add to what already exists, helping boost populations.
Enhancements take different forms and many of the simplest to implement provide critical cover. Cavities for roosting and nesting in dead tree stems can be rare or missing in forested environments, and many species benefit from man-made cavities, such as those provided by nest boxes.
Nest boxes are surrogates for abandoned woodpecker cavities. These are different than your typical “bird houses,” which are mostly non-functional for birds. They generally won’t open and have variably-sized entrance holes poking here and there around multiple levels of Victorian or Old West architectural micro-mimicry, and function maybe once, if that, for English sparrows. Most woodpeckers create their own new cavities each year and leave last year’s work for other critters to fight over. In many ecosystems with trees (forest, suburban or rural/forest edge), cavities are at a premium due to many factors, especially human activity.
We cut snags for firewood, safety worries, or during development and timber harvests. It takes many years for a tree to progress from fresh dead to broken, decayed and available for excavation, so these losses have a significant cost to our wildlife. Retaining snags, especially large ones, wherever possible is the best strategy, but boxes can help if properly constructed, placed, and maintained.
Northern flickers and hairy woodpeckers are common species in our Pacific Northwest human-dominated settings. This article describes an easy recipe for a simple box that mimics a woodpecker cavity being sought by secondary cavity species. These are suitable for cavity nesting birds such as chickadees, wrens, bluebirds, tree or violet-green swallows. Squirrels and flickers will sometimes expand the entrance holes out to fit their tastes, but that’s OK – they need a cavity too! Woodpeckers generally won’t use boxes, as they just have to make their own.
There are many designs out there, but all basically mimic a woodpecker cavity in dimension and proportions, so all are good – but some are better. I like this basic design from the Washington Department of Fish and Wildlife for simplicity and ease of construction. I recommend using such a design, so you can make them all the same and the parts are interchangeable. As your nest box network grows, it is easier to keep everything in good repair over time if they match.
Start with some 1” x 6” lumber, and a little bit of 1” x 8” for the roof. It does not have to be cedar because boxes will break or fall apart long before they rot. Making the roof a little wider than the top can help slow box decay. Lay the boards out and mark the lines using this handy-dandy, public-domain plan.
Drill your holes before cutting the boards. It is safer and easier that way. Entrance diameter is 1.5 inches, which is big enough for a chickadee or swallow and too small for a starling, the notorious non-native nest box interloper. Drill a few ¼” holes in the bottom for drainage if it gets wet inside. Sometimes a few holes for ventilation at the top of the sides are good, especially if the box is going in a sunny hot space where nesting season could be too warm for baby birds.
Cut the pieces. Use something to roughen up the inside of the door. I scratch it all up with a knife or awl. Make the scratches deep enough for a little bird to grasp. This can help fledgling birds climb out of the box. Smooth boxes can actually be a death trap when they can’t climb out. Some people use a router and make nice, even stair-step grooves.
Make the cut edge of the roof 1” x 8” at a slight angle so that the sloping roof more closely fits with the back. You can put a bead of caulk on this joint later to help seal the box. Or you can shorten the back piece, attach the roof flush across the top, and have the back extend below the box body where the holes are drilled for attachment. I think they are more stable if attached at the top and the bottom, however.
Assemble with screws, not nails. Over time, the boxes will almost certainly crack and warp somewhere and with screws you can replace pieces. It’s a good idea to pre-drill the parts with a small bit where the screws are going, as the wood is thin and will often split. I don’t always do this, and I usually regret it when a piece splits too badly to use.
Begin assembly with sides to the back. Then the bottom, then the door. The door gets two screws parallel to the opening. (The door can be the side or the front). These act as a hinge when cleaning. The top edge of the sides are sloped and when attached, need to be lined up at the top so the roof is reasonably straight. Part of the beauty of nest boxes is that birds are very forgiving of lousy carpentry! In fact, I think birds like boxes better when they are rough or crooked. Use bent nails as closures for the door. You don’t want it plopping open, which they do sometimes.
The roof should hang a little over all of the edges, hence the 1” x 8”. The top should be somehow coated to help resist water. I have taken to painting the roof white. Don’t use metal or asphalt shingles, as they may make the box too hot in sunny spots. (In the shady woods, this would be fine.) Old cedar shingles cut to the right size make great roofs; they’re rot-resistant and rough, with no need to paint.
The box body can be any kind of wood. If you paint them, just paint the outside so the inside is natural wood. I have heard from one small forest landowner and nest box aficionado in Northeast Washington that he prefers using particle board for his boxes. He thinks the animals like it better because it is rougher. And they weather until they are the same color as the forest and seem to disappear.
Larger versions of boxes can be built to attract squirrels, wood ducks, small owls, and barred or even great horned owls. Plans for these can be found at the WDFW Living with Wildlife website. These larger boxes should be mounted at least 8 feet up and have a much larger entrance. These can attract starlings if placed too close to habitation or farms, but this is not an issue out in the woods.
The classic wood duck box is roughly the dimensions of a pileated woodpecker cavity and are often used by squirrels and owls. In deep forest settings, I recommend mounting these larger boxes to enhance habitat for these forest cavity dwellers. The Foisie family in east King County had good success with tiny saw whet owls using their boxes (photo) which are mounted 15 to 18 feet up on the sides of Douglas-fir trees in a well-developed, mature forest stand.
Boxes can be attached to fence posts, sides of buildings (barns/sheds), deck and garden posts, installed posts, and trees. If you attach to trees, use long screws (deliberately not screwed all the way in) so they can be removed later, or aluminum nails. Don’t attach with anything big and steel, like 16 penny nails or spikes, as someday, someone might be cutting that tree with something, and you don’t want to put that rude surprise in the tree!
I think it is better to mount the boxes between 8 and 12 feet up, if you can get there, but it is a challenge to always have a ladder with you, especially if the boxes are well-dispersed through your forest. Mounting them at head height is usually fine, and many animals will gladly use them when mounted about 4 to 5 feet up. Then they are easy to clean out and you don’t have to carry, or fall off of, a ladder. Place small boxes at least 100 feet apart, and larger boxes at least 100 yards apart to allow for territoriality.
Speaking of cleaning: Many songbirds, such as tree swallows and bluebirds, bring lots of nesting material into the cavity. Grass, moss, feathers – you name it! But this material will get pretty poopy and full of bugs by the following spring. It is necessary to go out and clean out the small songbird boxes each fall, or early spring, and scrape this material out.
When you make your box rounds, this is an opportunity to make repairs (as needed) and even replace if one is in very bad shape. The larger boxes are usually mounted with a layer of dry wood chips in them. When cleaning these out, chips should be replaced every year or two, but there won’t be such a build-up of material. Large boxes still should be checked annually to look for needed repairs, and remove anything that might discourage use, including wasp nests.
Knock the wasp nests down unless you want to dedicate a box to wasps! Get this done before about April 1 so you don’t disrupt nesting.
Nest boxes are a wonderful enhancement tool for small forest landowners. I make a batch most years and end up giving them away or putting them up somewhere I can go back and keep up the maintenance. (We now have 35 on our property!)
They can last a long time. I’ve gone back to boxes I put up 25 years ago and found them weathered, but still functional, and full of material where birds had used them until they were packed. I emptied them, fixed the roof and put them back up! I have been keeping track of number of nests in my boxes at home, and last year something nested in every one of my boxes (except the one with the wasp nest).
I am convinced that box colonies become avian intergenerational habitat features, and the offspring of previous years return to breed in my boxes. That’s a reason to put up a few more each year. That makes me feel good.
I like nest boxes because it is something landowners can do. They work, and they are fun projects. Send pictures of your nest boxes and stories of what used them to ken.bevis@dnr.wa.gov!
foreststewardshipnotes.wordpress.com 