Walking North Chagrin Reservation's trails, you may notice the meadows are dotted with bluebird nesting boxes, their sides and tops weathered and gray. Occasionally, you may catch a glimpse of their occupants — eastern bluebirds, tree swallows, blackcapped chickadees and house wrens. The bluebird trail is a study in the nesting behavior of our local cavity nesting birds.
Bluebird Boxes and Early Decline
Although many different bird species use the boxes, they were first established in the park to help the eastern bluebird. Once a common rural songbird, the bluebird population began to drop in the early 1900s. Habitat loss, pesticide use such as DDT and competition with house sparrows and starlings were all blamed for the collapse. By the 1960s the population had plummeted by 90% in some areas.
Bluebird Nesting Behavior
The eastern bluebird's nest is built from dried grass and weeds with a lining of soft grasses where four to six pale blue eggs are laid. Bluebirds that nest successfully will remain paired and start a second brood. When a nest attempt is unsuccessful, the pair usually splits and one or both of the birds will travel to a new field. In northeastern Ohio, two broods per year are common, occasionally we may see a third attempt.
Tree swallows are identified by their metallic bluegreen backs and bright white chests. They're seen swooping in graceful arches over fields, gathering food on the wing. When courting, the male and female approach and rhythmically bow to each other on top of the nest box. These little birds actively defend their nest from predators — diving at your head if you venture too close. Their nest is made out of grass, and lined with feathers that hold four to six pure white eggs.
The male house wren's song is a bubbling warble and he places short straight twigs in prospective holes in his territory, whether they are a nest box, woodpecker hole or tree cavity. The twigs are four inches long and form the base of the nest, filling the hollow to the top. The female examines each potential nest site and chooses one. She then adds a lining of soft grass to the top of the nest where she lays several speckled eggs.
Normally, the chickadee nests in tree cavities and lines the decaying wood with plant fibers, moss and animal hair. Occasionally, they choose to nest along the bluebird trail. Chickadee eggs are dull white and heavily spotted. After each egg is laid the female carefully covers it with nesting material. She will continue to do this until her eight eggs are laid.
The lives of our cavity nesting birds are each unique and a joy to experience. The next time you’re exploring the trails and fields of North Chagrin Reservation keep an eye out for one of our bluebird trails. We ask that you don’t approach the boxes, but admire their charming residents from a distance.
Mindy Murdock, Naturalist, North Chagrin Nature Center
Mindy is volunteer coordinator for North Chagrin Reservation's bluebird box monitoring program.