Red-Eyed Vireo Facts

Red-eyed vireos are part of class Aves and can be found across North and South America in mixed and deciduous forests. They are migratory birds that travel long distances throughout the year. Their species name, olivaceus, is Latin for olive-green, which describes their olive feathers. Vireos are known as incessant singers that move in the canopy of forests and gather food by hover-gleaning, where they hover momentarily near leaves and pick up insects.

Description

Vireos are small songbirds with 10 inch wingspans and 5 to 6 inch bodies. As adults, they have dark red irides and are olive-green on the nape, back, wings, and tail with a white breast, belly, and throat. Their bills and legs are dark gray or black, and their bills are large and hooked. As adolescents, they have brown irides and a yellow wash on their under tail and flanks that may extend into the wing.

Habitat and Distribution

Their habitat is deciduous and mixed forests across North and South America. Vireos are found in canopies of forests and near streams and river edges that support hardwood trees. In fall migrations, they reside in the Gulf Coast pine forests and feed in its dense undergrowth. Their winter range covers the Amazon basin, inhabiting areas up to 10,000 feet high.

Diet and Behavior

Vireos’ diet changes based on the season, but it consists of insects and berries. In the summer months, they feed mostly on insects, including caterpillars, moths, beetles, bees, ants, flies, cicadas, snails, and spiders. In late summer, they begin to eat more berries, including elderberry, blackberry, Virginia creeper, and sumac. By the fall and winter, they are almost entirely fruit eaters. Vireos are foragers and gather food by picking insects from the foliage and undersides of leaves in the canopy of the forest.

Red-eyed vireos are migratory birds, performing two long distance migrations yearly between North and South America. During migrations, they travel in groups of up to 30 other vireos and may even travel with other species. They can spend most of their time in winter grounds in a mixed species group but become solitary during breeding season. Vireos are aggressive and have been known to chase or attack others of either sex. They are also a vocal species, with males singing up to 10,000 different songs in one day. Males sing songs that mark territory boundaries, and both sexes have a call that is used in aggressive encounters with other vireos or predators.

Reproduction and Offspring

Breeding season occurs from mid-April to August. Both sexes reach sexual maturity in less than one year. Males arrive at the breeding grounds in mid-March up to May to establish territories to pair with females once they arrive. Once the females arrive up to 15 days later, males sway their bodies and heads side to side, and then both birds vibrate their wings simultaneously. Males have been known to chase down potential mates, even pinning them to the ground. Once the male has found a partner, the female builds a cup-shaped nest out of grass, twigs, roots, spiderwebs, pine needles, and occasionally animal hair.

She then lays between three and five white, spotted eggs, each just 0.9 inches in size. Occasionally, females lay their eggs under a second layer of nesting to deter the parasitization of cowbirds. The incubation period is 11 to 15 days. Once they hatch, these young are born helpless, with eyes closed and pinkish orange skin. They are fed by both parents until they leave the nest 10 to 12 days later.

Conservation Status

Red-eyed vireos are designated as Least Concern by the International Union for Conservation of Nature (IUCN). Their population was determined to be increasing, with an estimated population of 180 million across North and South America.

Sources

• Kaufman, Kenn. "Red-Eyed Vireo". Audubon, https://www.audubon.org/field-guide/bird/red-eyed-vireo.
• "Red-Eyed Vireo". IUCN Red List Of Threatened Species, 2016, https://www.iucnredlist.org/species/22705243/111244177#population.
• "Red-Eyed Vireo". National Geographic, 2019, https://www.nationalgeographic.com/animals/birds/r/red-eyed-vireo/.
• "Red-Eyed Vireo Life History". All About Birds, https://www.allaboutbirds.org/guide/Red-eyed_Vireo/lifehistory.
• Sterling, Rachelle. "Vireo Olivaceus (Red-Eyed Vireo)". Animal Diversity Web, 2011, https://animaldiversity.org/accounts/Vireo_olivaceus/.