More about cavity-nesters
About 900 species of birds have been recorded in North America. About 80 are cavity-nesters. Historically, they have commonly nested in dead trees or trees with sections of wood decay.
Twenty species excavate their own cavities. All twenty are woodpeckers. They are called primary cavity nesters because they are capable of excavating in soft wood or other soft substrates.
Nest boxes for woodpeckers are most likely not advisable. Exceptions include when a species is federally or state listed or their population is in decline in a region. Safely retaining dead trees for woodpeckers is strongly recommended. Doing so supports their natural biology and benefits secondary cavity nesters (defined below) that later adopt their abandoned cavities.
Species that do not excavate their own cavities are considered secondary cavity nesters because they rely on found cavities. These species use natural cavities in trees, riverbanks, cliffs, or on the ground, such as under roots balls. Those that are small (e.g. songbirds and small owls) may adopt cavities vacated by woodpeckers. Woodpecker cavities can be found in trees (including some palms) as well as in saguaro cacti. Large cavity-nesting species usually rely on large, decayed holes in trees or on broken tree tops.
Some cavity nesters occasionally nest in locations other than tree cavities. Not all cavity-nesters accept nest boxes.
One-box-fits-all does not apply to cavity-nesters
Nest box for a large owl
Boxes should be designed specifically for species. The following are important considerations when providing nest boxes:
- Does the species need nest box support in your region?
- Is a species-appropriate habitat available for the box?
- Is the location safe from regular human disturbance?
- How great is the level of risk of predation?
- Can the box be placed at a height in a tree or on a pole suitable for the species’ preferences?