Blue-headed Vireo - Behaviour - Reproduction

Reproduction

When arriving to the breeding ground in mid-April, male Vireos will hold large, individual territories that can range from 1.5-6.6 hectares. Females will choose a male to mate with depending on the male’s ability to defend and control a large territory. While defending their territory from other males, the male Vireos will sing a primary song to attract females. Undecided females can usually be seen flying along the edges of competing male territories; usually this will force the two males into direct conflict for the right to copulate with the female.

Once a female has approached a suitable mate, the male will perform a series of mating rituals. Typically, these rituals involve the male building a courtship nest for the female. The courtship nest is not a full nest but is most likely an attempt by the male to display his ability to gather resources. Once the pair is established, the courtship nest is abandoned. Mating does not occur for approximately 2 weeks after pair has been established. During this time, the male and the female will cooperatively build a breeding nest which is typically formed between forking mid level branches of evergreen and deciduous trees and are composed of twigs and foliage. Breeding nests are not reused in following breeding seasons.

In one breeding season, a female will lay 3-5 eggs at a rate of 1 egg/day. Eggs are creamy white with brown or black spots and are 17-23.1 millimetres x 13.3-15.8 millimetres (0.055-0.075 in x 0.04-0.05 in). Eggs are incubated for approximately 14 days after being laid. Once hatched, infants are highly altricial, often having little to no downy feathers. Infants open their eyes during day 5 or 6 and will begin to fledge after 14 days for a total chick-rearing period of 28 days. Once the young are able to leave the nest, the parents will split the juveniles and separate. Juveniles are usually dependant on the parent to provide food for approximately 1 month after leaving the nest. If the nest is destroyed or a mating pair produces a failed brood, an attempt to re-nest may occur but this ultimately depends on when the brood fails. If the brood fails early on in the season, there is a higher chance that the pair will re-nest, if later, the pair will often separate and not attempt a second brood.

Blue-headed Vireo’s have an atypical breeding strategy when compared to other closely related species. Blue-headed Vireo males will assist their mates with daytime incubation of eggs, nest construction, and feeding of the chicks (Morton et al. 1998). Also, unlike most bird species, female Blue-headed Vireos do not attempt any extra-pair copulations with other males. Likewise, males make no attempt to guard females from other males, making Blue-headed Vireos both socially and genetically monogamous birds.