Reproductive biology

Migratory species pair up soon after their arrival on the breeding grounds in the spring, with the male delimiting and defending the territory by song. The open, cup-shaped nest is made of spider and silkworm webbing, fine grass stems, other plant fibers, lichens, mosses, and feathers. The nest is usually located at the fork of a branch, hanging below the place of attachment, either close to the ground or high in the canopy.

The clutch size is two to five, and the eggs vary in color from whitish to speckled. Both sexes share in incubating the eggs and caring for the young. The incubation period is typically 12-14 days, and the nestlings fledge at nine to 11 days. The fledglings cannot fly well at first but are good at scrambling on branches and in shrubs. They are fed by the parents for about three weeks after leaving the nest.

Migratory species try to nest two to three times each season. Nesting vireos are highly vulnerable to parasitism by species of cowbirds, and to predation by small mammals, snakes, and predatory birds.

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