Song sparrows are known to be monogamous with occasional polygyny being observed. Males have not been reported to feed their mates. Males arrive ahead of females on the breeding grounds and begin to define their territory by puffing out their plumage, extending and fluttering their wings, and by singing from three or four main perches. Males announce their identity by territorial singing and aggressive behavior. Females announce their identity by either a high pitched note, or a nasal kind of chatter. Pair bonding occurs on the territory of the male. Females select mates, probably based on the quality of his territory. Males show readiness to mate by pouncing near their mate. They will also pounce near neighboring females while their mates are not close by. Females are more faithful to mates and reject advances of strange males while their mates come to their defense. Females will 'henpeck' their mates by opening her bill at him and giving him small pecks.
Mating System: monogamous ; polygynous
Typically all females and most males start breeding at age one. The breeding season begins in April and ends in August. Females build a nest in 5 to 10 days. The nest is made of dead grasses, weed stems, roots, and bark shreds formed into a cup with rough outer layer lined with finer grasses and sometimes hair. The nest is usually placed at the base of shrubs or clumps of grass. Females lay between 3 and 5 oval shaped, light blue or greenish-blue, spotted eggs.
Breeding interval: Song sparrows may breed once or twice during a breeding season.
Breeding season: Song sparrows breed from April through August.
Range eggs per season: 3.0 to 5.0.
Range time to hatching: 12 to 14.0 days.
Range time to independence: 18 to 20 days.
Average age at sexual or reproductive maturity (female): 1.0 years.
Average age at sexual or reproductive maturity (male): 1.0 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization
Average eggs per season: 4.
Females incubate the eggs for 12 to 14 days. The young are tended by both male and female for the first 5 to 6 days, although females are more commonly observed at the nest. The young open their eyes at 3 to 4 days, they can fly well at 17 days, and are independent at 18 to 20 days.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)