The Eastern bluebird, Sialia sialis, is one of the most beautiful U.S. songbirds. Bluebirds are one of the rare bird species displaying juvenile dimorphism, meaning that males and females can be distinguished even before they reach maturity.
The male is 7 inches long, while the female is 6 1/2 inches long. The male’s weight is 1 to 1.1 ounce, with the female being slightly heavier.
A male has a brilliant blue head, nape and back, with a warm reddish-brown-colored breast and white on the lower belly. Female markings are similar, but the color is somewhat muted. The female also has a white eye ring, states Bluebird Hollow, a website dedicated to information about the species.
Bluebirds have both loud and soft songs. The male bluebird sings loudly when looking for a mate, when nesting and also to warn of danger. Females have been observed singing loudly when the male is not close by and there is a predator. Males use the soft song as an assurance to the female during egg-laying time.
The bluebird call, “tu-a-wee,” is made by males, females and juveniles as a contact signal between family members.
The male does not assist the female with nest-building or incubating. After the chicks hatch, the female parent performs almost all of the feeding.