WITH SPRING HERE, birds and other animals are looking for places to build nests. Many species, such as chickadees, are "cavity nesters." That is, they typically nest in holes in dead or dying trees, which are sometimes referred to as "cavity trees" or "wildlife trees" because they are so valuable for wildlife.
Unfortunately, cavity trees are getting harder and harder to find. So humans often try to help by offering artificial cavities, otherwise known as "nest boxes" or "bird houses." Chickadees, which routinely win contests to see which is "America's favorite backyard bird," are often willing to use a nest box.
I've seen chickadees nest in a badly designed box that was located on someone's front porch, right next to the front door. But that was probably because there were not enough other suitable nest sites in the area. When they have alternatives, chickadees are generally choosy about which nest boxes they'll use.
Stores often have very cute nest boxes for sale, but the cutest boxes may not be the best choice. Each type of bird has special needs, so a nest box designed for one type of bird will not necessarily suit another.
A nest box for black-capped chickadees should be about 9 inches deep with the entrance hole at the top of the box (about 7 inches from the bottom); the floor should be about 4 inches by 4 inches. The entrance hole should be from 1 inch to 1 1/8 inches in diameter. A perch isn't necessary and, in fact, should be removed if the box came with one (because perches give nest predators a place to stand.
In addition, any nest box should have drainage holes so that water doesn't collect in the bottom and ventilation under the roof so that heat can escape. The tall, deep style of box is best for most birds because predators have a more difficult time reaching the eggs and babies. If the entrance hole is larger than an inch and a half, the box will probably be used by starlings if they are in your area.
If you feel inspired to paint your nestbox, as many people do, consider the possibility that a brightly colored nestbox might attract more predators than one that blends in with the scenery. Color also affects the temperature inside the nestbox: A dark-colored nestbox will stay warmer than a light-colored nestbox will. Which is better would depend on your climate and where you plan to put the nestbox.
Once you've selected a box that's well designed for chickadees, your next job is to find the best place to put it. The recommended way to install a nest box for black-capped chickadees is to place it 6-15 feet high on the edge of an area where there are mature trees. The box should receive about 50% sunlight throughout the day. If possible the entrance should face away from prevailing winds, so that rain isn't blown into the box during storms.
Even if you are able to place a nest box perfectly, birds often seem to ignore a nest box for its first year. Most people recommend that you leave a nest box in position for two years--then, if it's still not being used, move it to another location.
Most people say that nest boxes should be cleaned at least yearly, if not after every brood. This helps to prevent buildup of parasites that otherwise might undermine the health of young birds.