Black-headed grosbeaks are monogamous. Males arrive in the spring about six days before the females, remaining solitary until the females arrive. Males sing to establish territory and attract mates. Older males get higher quality territories, and fighting for territory can be aggressive, as black-headed grosbeaks attack swiftly during flight. Once females arrive, males will sing from perches near females, occasionally flying up into the air while singing a courtship song.
Mating System: monogamous
Black-headed grosbeak females build a nest between 4 and 25 feet above the ground over a period of 3 to 4 days, usually in deciduous trees; especially willows and coast live oaks. The nest could also be located in shrubs, bordering streams, or more rarely, gardens and parks. The nest itself is constructed thinly and loosely with twigs, rootlets, and other plant materials and placed in the dense outer foliage of a tree or shrub near an opening.
Black-headed grosbeaks produce one brood per year in the spring and early summer, from April to July. They lay 2 to 5 eggs per season. The eggs vary in color from greenish or bluish to spotted brown. Eggs hatch in 12 to 13 days with all eggs hatching within a 24 hour period. Young fledge after about 12 days, becoming independent after another 14 days. Females reach reproductive maturity around 1 year, while males mature after 3 years.
Breeding interval: Black-headed grosbeaks produce one brood every year.
Breeding season: Copulation and nesting for Pheucticus melanocephalus occurs from April through July.
Range eggs per season: 2 to 5.
Average eggs per season: 3-4.
Range time to hatching: 12 to 13 days.
Range fledging age: 11 to 15 days.
Range time to independence: 23 to 30 days.
Range age at sexual or reproductive maturity (female): 1 to 1 years.
Range age at sexual or reproductive maturity (male): 2 to 4 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Average eggs per season: 3.
Both sexes invest time incubating the eggs, alternating sitting periods throughout the 12 to 13 days of incubation. Occasionally, both parents will sit on the nest and sing simultaneously. In a similar fashion, both parents feed their nestlings, and females occasionally use song to communicate with their young. Males depart for breeding grounds earlier, leaving females to feed their fledged young.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)