Tuesday, 16 August 2011

Black-headed Grosbeak

Females build nests among the dense foliage on an outer branch of tall broadleaved trees or shrubs, 3–35 feet above ground. They will occasionally build in dense shrubs such as blackberry. The nest is in the shape of an open saucer, made of fine grass, rootlets twigs, bark and conifer needles. It is often lined with rootlets, hair, and fine plant material. The female lays 2–5 pale green, blue or grey eggs that are spotted with reddish and dark brown. The eggs are incubated by the male and female for 12–14 days. After the eggs have hatched the fledglings leave the nest in about 11 or 12 days, however they are unable to fly for another two weeks. The young are fed by both adults. The Black-headed Grosbeak's monogamy is under study, but pair bonds generally last for only one breeding season. They typically have one brood per season, though double broods have been documented in foothills of the Sacramento Valley in California.