The young have spotted breasts until the fall molt when all bluebirds grow dull feathers for protection from predators. The males are bright blue again by spring.

As early as March or as late as June, the male bluebird locates a nesting site, establishes a territory around it, and sings to attract a female and warn other male bluebirds to stay away. Bluebirds are very territorial during nesting season and typically will not build within 100 yards of another bluebird nest.

Once a female accepts a site, she will do most of the nest building. She builds a neat cup nest of dry grasses or pine needles. Nest building may take five days to three weeks.

The female lays one blue (or rarely white) egg each morning until three to six eggs are produced. Incubation begins after the last egg is laid. Thirteen to fourteen days later, after incubation, all will hatch within hours of each other.

Five blue eggs in grass nest
Photo by Liz Schmid

Both the male and the female adults tend to the nestlings. They feed the nestlings with soft insects graduating to courser foods as the nestlings grow. Each nestling is fed about every 20 minutes.

The adults keep the nest clean by removing the fecal sacs which enclose the nestlings' waste. The young grow rapidly. Their eyes open on the eighth day.