BIRDwatch

Eastern Bluebird

By Cecily Nabors

Royal blue on his back, rusty red on his breast, a male Eastern Bluebird (Sialia sialis) looks ready to fly over that fairytale rainbow. Females’ coloration is more subdued but still lovely. This sweet, small member of the thrush family is always a treat to see. But what color is a bluebird? It’s not a trick question! The answer is, it depends. In bird feathers, blue is a structural color, not a pigment. The feathers’ construction, and the tiny spaces within their filaments, reflect only the blue wavelengths of light. In dim light or when backlit, the bird may merely look dark. When Henry Thoreau wrote, “The bluebird carries the sky on its back,” he was right; like the sky, a bluebird sometimes looks gray, but it’s usually a brilliant sky-blue. Eastern Bluebirds favor low perches from which to search open ground for insects, so they’re partial to areas with scattered trees and short vegetation. Pastures and meadows, orchards, hikerbiker trails, golf courses, and open areas in parks are all good places to hunt for them. If you hear a soft, melodious warble, look around for a flash of blue. Both males and females sing, but males are louder (no comment). In our Mid-Atlantic area, we are privileged to see bluebirds all year; our winters are usually not cold or snowy enough to keep them from finding food. Their main diet is insects such as beetles and grasshoppers, but in fall and winter, bluebirds eat large amounts of fruit, including black cherry; hackberries; and the berries on holly, dogwood, pokeweed, and juniper. They will sometimes supplement with their diet meat like worms or tree frogs. If you see a bluebird drop from a perch, grab an insect, and fly off with a beak full of flutter, the bird is probably carrying food for its young. Eastern Bluebirds are cavity-nesters, often using old woodpecker holes. Bluebirds suffered after the introduction of the much more aggressive House Sparrow and European Starling. Nest theft by these two nonnative species, combined with pesticides and changes in habitat, sent bluebirds into sharp decline until humans intervened. For information about how Dr. Larry Zeleny sparked the building of bluebird nest-boxes to save the species, check out the North American Bluebird Society at www.nabluebirdsociety.org. During courtship and nesting, Eastern Bluebirds lose their shy, confiding air and claim their chosen tree cavity or nest box with lots of song and chasing off intruders. Males seek out suitable spaces, while females choose among those offered. Individuals appear to have strong preferences for particular types of nest site, according to the Cornell Lab of Ornithology, with older birds more likely to choose a nest box than a natural cavity. The female (pictured below) does most of the nest-building and incubates the eggs. At night, the male may stay at the nest with the female, after bringing her some food. The young are fed with caterpillars and soft insects. When the first brood fledges, the parents may build another nest in the same cavity. Occasionally, one of the young from the first brood will act as a “helper at the nest,” bringing food to the second set of nestlings. A pair of Eastern Bluebirds may bond for several years. However, studies suggest that females sometimes breed with more than one male (no comment). Suburban yards may not have enough open area to appeal to bluebirds in breeding season, when a large supply of insects will be needed to feed the everhungry young. In fall and winter, though, other food sources such as a plentiful supply of fruit and berries assume a great importance. Planting shrubs and small trees such as American holly, juniper, pyracantha, and the native dogwoods will help entice bluebirds to local gardens. In winter, bluebirds will also visit birdfeeders. Most books advise providing mealworms to coax bluebirds to the feeder area, but they will also come readily to suet and shelled peanuts. When the view from the kitchen window across a wintery yard includes a beautiful Eastern Bluebird, a gardener can truly enjoy that “bluebird of happiness.” o

Cecily Nabors is a retired software manager who has been watching and counting birds for much of her life. She publishes the GoodNatured Observations blog at cecilynabors.com.