Unlike birds that build their nests in the branches of trees or in thick foliage, some species prefer to nest in hollow cavities. These birds are known as "cavity-nesters." Woodpeckers are primary cavity-nesters as they can excavate their own nest sites in dead trees. Secondary cavity-nesters like Bluebirds, Chickadees and Titmice lack the jaw and beak strength to do this, so they must rely on old woodpecker holes and naturally occurring cavities to raise their young.
Sadly, natural cavities have been in steep decline for many years. Much of the ideal habitat containing dead and dying trees has been replaced by shopping centers, subdivisions and highways. Even in our own backyards, a dead tree is considered unsightly and dangerous and is usually removed.
Competition among birds for the remaining nest sites has increased, compounded further by exploding populations of non-native House Sparrows and European Starlings, themselves cavity-nesters. Many native birds are forced to nest in less than ideal cavities, where predators and weather are more likely to take their toll.
Adding a nestbox to your habitat helps offset these imbalances and increases the breeding success of birds. In addition, a nestbox provides an exciting opportunity to enhance the environment and to observe and enjoy your native cavity-nesting birds.