Whether you buy a birdhouse at a retail store or make your own, several factors increase the likelihood of a successful fledging. Some bird box designs are known to improve the likelihood of brood success, while others may contribute to the unfortunate death of the chicks. A good quality birdhouse should have each of the following features.
1. Beginning staircase or textured front wall
Inside the front wall of each birdhouse, the chicks need a ladder or a textured surface to stick their tiny claws into. They must be able to climb up to the entrance hole to fledge. If your birdhouses are made of very smooth materials, it will be necessary to etch horizontal grooves, forming a ‘ladder’ for the chicks to climb. Simply make tiny lines about 1/2″ to 1″ apart, using a chisel, woodcarving knife, or other similar instrument, in a horizontal pattern from the bottom of the box to the entry hole. You can also attach 4″ x 4″ square window screen or other fine mesh with wood staples or carpenter’s glue. Just make sure the mesh isn’t too rough and the staples don’t stick out. If you use glue, make sure it is completely dry before allowing the birds to occupy the house.
2. Smooth and safe entry holes
Birds are diligent in keeping their feathers in excellent condition. Their lives depend on it. If the entrance hole is jagged or has sharp bumps, this will damage the feathers every time a bird enters or exits the box. Run your fingertip around the entrance hole of your birdhouse. If you feel any roughness, sand it down with fine-grit sandpaper. This should be done every year when you clean out the old nest. If the entrance hole has been affected by a squirrel, you may be able to fit a hole protector over the top. These can be purchased or made at your own store by simply cutting a thin square of wood and drilling the appropriate size hole inside. Secure the shield over the old, damaged hole with screws, taking care to prevent the screws from penetrating into the interior of the box, where they may present a plume hazard. Alternatively, you can attach the guard with carpenter’s glue.
3. Ventilation and drainage holes
Without airflow, bird boxes can get too hot or the air may not be healthy for young birds to breathe. The intake hole itself doesn’t provide enough fresh air, so you should add some vents if they’re missing from your design. Ventilation holes should be located near the top of the box, preferably under the protective lip of a protruding lid.
If the nest box has holes in the bottom, they are not for ventilation; They are for drainage. These are also essential. Drainage holes prevent the boxes from filling in the rain and help keep the nests dry if they do get wet. Some species, such as bluebirds, don’t mind if their nests get wet periodically. Check for holes in the floor of the box. They can be located in the middle or in the corners. If there are no drainage holes, make them with a drill. Weep holes can be 1/8″ to 1/4″ in diameter. Sometimes the holes become clogged with debris from the nest, so make sure there are enough holes to allow for that possibility.
4. Properly taped roof seams
A good birdhouse design should not have leaky roof seams, but don’t despair if you have one that does. If there is a seam in the roof that allows water to enter, it may be fine for bluebirds, as long as only a few drops of water enter during a heavy storm. However, if it rains heavily, the box can fill up faster than it drains, drowning or chilling the unfortunate chicks. Inspect roof seams for possible leaks and fill them with a bead of exterior caulk. Make sure the caulk is completely dry before putting it outside. If a bird gets caulking materials or glue on its feet or feathers, it can cause death.
5. Human access for cleaning
All bird houses should be properly maintained. This can usually be done once a year, after the chicks have left. To do this, it is necessary to access the inside of the box, without having to disassemble or break it. Some decorative bird houses may not have this feature as they are purchased more for ornamentation than practical purposes. The best designs open to the sides or front. This is easier for you and less dangerous for wild birds. When the floor of the box is the access point, there is a risk that it will accidentally open and dislodge the occupants. When the entrance is the roof, there is an increased risk of occupants getting wet in a major rain storm, although this is easily avoided by following the steps in #4 above.