Barn swallows are socially monogamous (one male mates and raises chicks with one female). However, barn swallows often copulate with other swallows that are not their mate. Therefore, they are probably actually polygamous. Barn swallows form breeding pairs each spring after they arrive on the breeding grounds. They form new pairs each spring, though the same two birds may nest together for several years.
Male barn swallows try to attract females by displaying their tails and singing. Female barn swallows seem to prefer males with long tails that are equal lengths on each side. Long tails and symmetry may be good signals of a male's health and fitness as a mate.
Adults that don't have a mate sometimes join breeding pairs, and help them to build a nest, defend the nest, incubate the eggs and brood the chicks. These "helpers" are usually male. They may mate with the female of the nest.
Mating System: monogamous ; polygynandrous (promiscuous) ; cooperative breeder
Barn swallows usually breed between May and August. They usually raise two broods of chicks each summer. The male and female work together to build a nest. The nest is built of a mud shell, and is lined with grass and feathers. The female lays 3 to 7 eggs (average 5). Both parents incubate the eggs, which hatch in 13 to 15 days. The chicks are naked and helpless when they hatch. Both parents feed and protect the chicks, as well as removing their fecal sacs from the nest to keep it clean. The nestlings stay in the nest for about 20 days. When they are handled by humans they tend to leave the nest at least a day too early. The parents continue to care for the chicks for up to a week after they leave the nest. They feed them and lead them back to the nest at night to sleep. By two weeks after they have fledged from the nest, the chicks have left the area. They often travel quite far, visiting other barn swallow colonies. Young barn swallows are able to breed in spring after they hatch. Young barn swallows generally do not lay as many eggs as older birds.
Breeding interval: Barn Swallows usually produce 2 clutches per season, breeding seasons occur once each year.
Breeding season: Barn Swallows breed from May to August.
Range eggs per season: 3 to 7.
Range time to hatching: 13 to 15 days.
Average fledging age: 20.50 days.
Range time to independence: 2 (high) weeks.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Average eggs per season: 4.
In North America, both barn swallow parents incubate the eggs and feed the nestlings. However, females provide more parental care than males. During the nestling period, barn swallow parents may feed their chicks up to 400 times per day. Barn swallows feed their chicks a compressed pellet of insects that they carry in their throat.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents
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