By Megan Hart, Park Biologist

Dead and declining trees may seem like an eyesore. However, they are an important habitat component for cavity-nesting birds. Cavity nesting is a reproductive strategy used by some species to protect their nests from weather and predators. There are two types of cavity nesting birds: primary and secondary. Primary cavity nesters are those that excavate nesting holes. Secondary cavity nesters are those that rely on abandoned cavities created by primary cavity nesters. 

Woodpeckers are a great example of primary cavity nesters. They are excellent at excavating holes by using their chisel-like beaks to chip away for several days until the cavity is complete. Woodpeckers are considered keystone species by providing shelter and nesting sites for other wildlife. There are seven species of woodpeckers that breed in Lake County. The most common are the northern flicker, downy, hairy, red-bellied and pileated woodpeckers, which are frequent backyard visitors. The more uncommon yellow-bellied sapsucker breeds in young northern deciduous forests. Sapsuckers get their name from feeding on the sap from the rows of holes they drill in trees. Our other uncommon species, the red-headed woodpecker, was once more widespread but has declined with the destruction of mature forests with dead trees and nut crops, which has led to it being listed as a species of concern in Ohio. 

Woodpeckers like this northern flicker are a great example of primary cavity nesters.         

Secondary cavity nesters rely on previously excavated holes. Black-capped chickadees, tufted titmice, and white-breasted nuthatches are some of our favorite backyard visitors that take advantage of these preexisting cavities. Eastern bluebirds used to also rely heavily on old woodpecker cavities for nesting sites. However, their numbers began to decline due to competition with non-native European starlings and house sparrows, which led to the widespread use of bluebird boxes to help their populations. Similarly, purple martins used cavity trees along forest edges and rivers but have since moved almost exclusively to human-made structures for nesting. Other bird species like the great crested flycatcher, prothonotary warblers, and tree swallows take advantage of both tree cavities and nest boxes that can mimic cavity-like conditions.  

Secondary cavity nesters like this white-breasted nuthatch rely on previously-excavated cavities. 

It isn’t only small songbirds that utilize tree cavities. Waterfowl like wood ducks, hooded mergansers, and common mergansers utilize tree holes and waterfowl boxes for nesting. American kestrels, barred owls, barn owls, and eastern screech-owls also use available tree cavities and nest boxes for roosting and nesting. Other wildlife like squirrels, raccoons, bats, and opossums rely on abandoned cavities for shelter and rearing young. 

Raccoons often rely on abandoned cavities for shelter and rearing young.

The main reason for cavity-nesting bird declines is a lack of dying and dead trees being left standing on the landscape. Dead trees left in areas away from buildings, trails, and other human-used places is a wonderful way to promote wildlife. A secondary option is to provide artificial cavity structures, like wood duck, bluebird, owl, purple martin, kestrel, and bat boxes, to encourage secondary cavity users to inhabit your landscape. Lake Metroparks has nesting structures through the park system to help encourage habitat use by these species. 

Eastern bluebirds often rely on human-made cavity-like structures due to housing competition from non-native species.

Great parks to observe cavity-nesting birds are Chagrin River Park, Veterans Park, Hidden Lake, Penitentiary Glen Reservation, Girdled Road Reservation, and Indian Point Park, but you can find many species at any of the parks. Get out and explore!