Both sexes arrive at breeding sites at the same time following migration and males establish territories shortly upon arrival. Pairs form within 7 days, and nest building (on the ground, usually under or near shrubby vegetation) begins in mid June. Harris's sparrows are a monogamous species, but length of pair bond is currently unknown. Some research has shown slight site fidelity, with males more likely to return than females and both are more likely to return to a successful breeding site. It is unknown whether successful breeding pairs reunite in subsequent years.
Mating System: monogamous
Harris's sparrows breed from late May or early June until August. They begin laying their eggs 14 days after arrival to the breeding site. They lay 3 to 5 (4 to 5 average) eggs per clutch, and one clutch per season. The eggs take 13 to 14 days to hatch and chicks are born weighing about 3.1 g. Chicks fledge after 8.5 to 10 days and they reach independence after two more weeks.
Breeding interval: Harris's sparrows have 1 brood per year.
Breeding season: Harris's sparrows breed from late May or early June to August.
Range eggs per season: 3 to 5.
Average eggs per season: 4-5.
Range time to hatching: 13 to 14 days.
Average birth mass: 3.1 g.
Average time to independence: 2 weeks.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Nests are built either out in the open or under low shrubbery with minimal insulation, so to keep the egg temperatures in optimum range the female spends long stretches sitting on the nest. Females incubate eggs for about 80% of the day, increasing or decreasing in response to ambient temperature. Both parents feed the nestlings, though first-year breeding males take longer than second-year breeding males to initiate this behavior. Offspring are dependent on their parents for two weeks post fledging.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)