As winter relaxed its grip earlier this month, six consecutive days of bright sunshine and blue skies left no doubt that spring was on its way.
Red maple buds burst open, and a pair of eastern bluebirds began visiting a nest box on the edge of the yard. They were just beginning to investigate and evaluate potential nest sites.
First, the duller female landed on the top of the box and then hopped down to the entrance hole. She stuck her head in a few times and then disappeared into the box. She did this several times. Then the bluer than blue male inspected the box. It’s impossible to know why, but clearly they found the box appealing.
Perhaps it was because they successfully raised two broods in it last year. In any case, they repeated this behavior on each of the recent warm sunny days. They haven’t yet carried any nesting material to the box, but that will come — possibly this week. I look for the season’s first bluebird eggs in early April.
I remember that on my wife’s birthday (April 6) one year, we had a heavy wet snow fall, and one bluebird nest had four eggs. My notes remind me that it was 1988, and the nest was ultimately successful.
After 30 years of building and monitoring nest boxes, bluebirds are one of my favorite birds. Though I never saw one as a child, my mother often reminisced about the bluebirds she saw when she was young in the 1930s.
I suspect it was why blue was always her favorite color. By the time I grew up in the 1950s and 1960s in southeastern Pennsylvania, bluebirds were rare. Pesticides contaminated their invertebrate foods, and nesting cavities were in short supply. I didn’t see a bluebird until I was 26. Since the first Earth Day in 1970, however, the use of broadly toxic chemicals has been restricted, and we’ve discovered the bluebird’s willingness to use man-made nest boxes.
Today, bluebirds are common in suitable habitat — open areas with scattered trees. Pastures, hayfields, cemeteries, and golf courses are ideal. The easiest way to attract bluebirds is by supplying nest boxes. The key is placing them in suitable habitat. Bluebirds prefer open areas with scattered trees and few houses.
Pastures, hayfields, cemeteries, and golf courses come to mind. Males sing from treetops, and both sexes hunt from elevated perches.
They watch the ground for grasshoppers, beetles, and other insects. They capture prey by flying to the ground, pinning the insect with their feet, and killing it. Then they return to the perch for the meal. A basic box measures four by four inches and is 10 to 12 inches high.
The entrance hole should measure precisely an inch-and-a-half in diameter and be placed about an inch from the top. This hole size excludes bigger-bodied starlings from entering the boxes. Extend the roof at least 3 inches beyond the front of the box to protect the entrance from driving rain. The front should flip open for easy cleaning.
Hang nest boxes 4 to 5 feet above the ground on a post protected from below by a predator baffle. The baffle could be a piece of large diameter PVC pipe, an inverted sheet metal cone, or a piece of eight-inch stove pipe. The baffle is essential because, without it, a nest box eventually becomes a feeder for raccoons and rat snakes.
Space nest boxes about 100 yards apart to minimize territorial squabbles.
A bluebird nest is a simple cup of grass or pine needles. Sometimes it’s just a couple inches deep; sometimes it extends up to the entrance hole. The eggs, typically four or five per clutch, are just what you might expect — sky blue (though one in 20 are white) and a not quite an inch long. They hatch in about 14 days.
Young bluebirds leave the nest 16 to 21 days after hatching. Bluebirds typically raise two broods and sometimes three, so it’s not unusual to have active nests from April through August.
For bluebird box plans, visit www.nabluebirdsociety.org/eastwestbox.htm. If you’re not a do-it-yourselfer, bluebird nest boxes can be purchased at wild bird stores and nature centers.