Throughout their summer range, Red-eyed Vireos breed in deciduous and mixed forests with shrubby understories. Numbers are greatest away from forest edges and near small openings in the interior forest canopy. In the pine forests of the southeastern United States, they prefer stream and river edges supporting hardwood trees. In northern areas, breeding territories in alder thickets and aspen groves are common. Red-eyed Vireos can sometimes be found in residential areas, city parks, and cemeteries with enough large trees. During migrations, they use a larger variety of forest habitats. Still preferring broadleaf forests to conifers, they will make use of forest edges, citrus groves, city parks, suburban residential areas, and other areas with scattered trees. During fall migrations, they rest and feed in Gulf Coast pine forests with dense undergrowth. In their winter range in the Amazon basin, they inhabit a variety of habitats up to 10,000 feet elevation. Rainforest, mangroves, plantations, second-growth forests and forest edges, arid regions with adequate vegetation, and even gardens with scattered trees and shrubby clearings can serve as winter homes.Back to top
Red-eyed Vireos eat invertebrates as well as seeds and fruits. Their diet changes substantially throughout the year: it’s mostly insects during summer, especially caterpillars which can account for 50% of their summer diet. Caterpillars make up only 15% of their spring diet, and 20% in fall. They also eat butterflies and moths, beetles, mosquitoes, flies, bugs, cicadas, wasps, ants, bees, and sawflies, to (less frequently) grasshoppers, crickets, dragonflies, and damselflies. They'll also eat spiders and small snails. Smaller prey are eaten whole. Caterpillars and other larger meals are trapped under a foot and plucked apart into bite-sized bits. Among plant foods, small wild fruits like blackberries, elderberries, spicebush, Virginia creeper, sassafras, dogwood, arrowwood, and bayberry outnumber the occasional flowers, leaf buds, and magnolia seeds. As fall migration approaches, the amount of fruit in their diet rises. During migration they eat both insects and fruit, but are almost entirely fruit-eaters on their wintering grounds in South America.Back to top
The female chooses a fork in a branch of a midstory to understory tree or shrub. The fork is typically shaded, concealed from above by vegetation, and far enough from the trunk to provide an unobstructed 360 degree view. Most nests are in deciduous trees, at an average height of 10 to 15 feet.
The female spends 4 to 5 days constructing a nest of bark strips, grasses, pine needles, wasp-nest paper, twigs, and plant fibers that hangs below the branch. She glues the materials (some of which are provided by the male) together and to the branch fork with spider-web adhesive, occasionally supplemented with spider egg cases and sticky plant fibers. The open cup is usually just over 2 inches across and an inch and a half deep, surrounded by half-inch walls and supported by an inch-thick floor.
|Clutch Size:||1-5 eggs|
|Number of Broods:||1-2 broods|
|Egg Length:||0.8-0.9 in (2-2.4 cm)|
|Egg Width:||0.5-0.9 in (1.2-2.4 cm)|
|Incubation Period:||11-15 days|
|Nestling Period:||10-12 days|
|Egg Description:||Dull white with sparse, sepia speckling.|
|Condition at Hatching:||Born helpless, with eyes closed and sparse down on the pinkish orange skin of their heads, backs, and wings.|
Breeding males sing incessantly from before sunrise until well into the afternoon, usually from treetops around the periphery of their territories. Challenges provoke posturing, chasing, pecking, grappling, and displacing rivals from perches. Females and males indicate threats by raising crown feathers, fanning tails, and opening the bill while pecking and calling. Males also threaten by tilting their bodies forward and thrusting their heads out. The female aggressively defends the nest. She and the male will swoop, snap, and peck at intruding jays, crows, squirrels, and chipmunks. Both chase, scold, and strike intruding cowbirds with their wings. But once cowbird eggs are in the nest they are generally tolerated, though the vireo parents sometimes cover the intruder’s eggs with additional nesting material. Red-eyed Vireos hop along and flit between branches when foraging. They glean most of their invertebrate food from the underside of leaves. Pairs are seasonally monogamous. The female builds the nest, incubates the eggs, and broods the young. The male offers nest materials and feeds the female, especially during incubation. The female begs for food away from the nest, quivering her wings, opening and closing her mouth, and calling, much like a begging chick. She solicits copulation by calling and crouching with wings quivering and tail spread and lowered. Both mates vibrate wings and twitter during copulation. Both may join large mixed flocks during migrations and on wintering grounds.Back to top
Red-eyed Vireos are numerous and despite some local declines, overall populations increased by approximately 0.6% per year between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 130 million and rates them 6 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. These birds are sensitive to disturbances such as clearcut logging, strip mining, and forest fragmentation. Logging practices that leave smaller canopy openings are less disruptive. Red-eyed Vireos are among the most common hosts to Brown-headed Cowbird eggs. Nest parasitism is more frequent near forest edges. Local populations show growth during the breeding season after large caterpillar outbreaks. Like many nocturnal migrants, Red-eyed Vireos are killed in collisions with buildings and other tall structures, sometimes in large numbers.Back to top
Cimprich, David A., Frank R. Moore and Michael P. Guilfoyle. (2000). Red-eyed Vireo (Vireo olivaceus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.
Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.