Sometimes confused with bird feeders by novice birders, bird boxes are simple structures built to provide a safe place for breeding pairs to nest, lay eggs, and raise their young. They also serve as a cosy shelter for overwintering birds. For this reason, bird boxes are also referred to as nest boxes, bird houses and roosting boxes.
As with feeders, bird boxes come in a variety of shapes and materials. However, all bird boxes feature a single entry hole to protect the birds from larger predators. Boxes with smaller holes around 25 mm in diameter provide safety for tree nesting birds finches, wrens and tits, while holes of about 35 mm can house woodpeckers and other larger birds.
A good bird box will feature solid construction with walls about 20 mm thick, be absent of any perches that might attract predators, and have an optimally sized entry hole for the particular species a birder wishes to attract. The entry hole can also be reinforced with a plate to prevent larger birds from pecking to enlarge the opening. For easy cleaning, wooden boxes should have a removable side panel or door that lifts.