Adult Vireo olivaceus are occasionally preyed upon by sharp-shinned hawks. Eggs and nestlings are significantly more vulnerable than adults and are predated by many species including American crows, blue jays, common grackles, eastern chipmunks, and red squirrels. Red-eyed vireos employ aggressive swooping and pecking to deter predators. Some incubating females crouch into the nest, remain motionless, and rely on their olive coloration as camouflage. Both males and females produce catbird-like mews or "myaahs" when intruders near their nests.
Known Predators:
Anti-predator Adaptations: cryptic
Vireo olivaceus is a vocal species that is frequently heard calling from the upper forest canopy. Their primary call is mostly two-note phrases that are mnemonically described as "Look up! See me? Over here! Do you hear me?" Male red-eyed vireos are one of the most persistent singers of all birds and have been recorded singing 10,000 songs in one day. These songs are used to delineate territory boundaries, and are only sung by males. Both sexes use a call described as a catbird-like mew usually used in aggressive encounters or when predators are near.
Vireo olivaceus also uses postures and body movements to visually communicate. These postures have been identified as Crest-erect Alert, Head-forward Threat, Tail-Fanning, and Gaping displays. All of these displays are used in aggressive encounters between either sexes and are usually followed by pecking if an individual does not retreat. Like all birds, red-eyed vireos perceive their environments through auditory, visual, tactile and chemical stimuli.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Currently, Vireo olivaceus populations are stable and distributed across a wide geographic range. For these reasons, they are of least concern to conservation organizations. As migratory birds, red-eyed vireos are protected under the United States Migratory Bird Act. Although these birds are currently abundant and can tolerate low levels of habitat destruction, large-scale habitat changes can result in local extinctions. Red-eyed vireos have been shown to tolerate selective harvesting or small areas of clear-cutting that only cause small canopy openings. Any activity that significantly reduces canopy cover (extensive clear-cutting, strip mining, cultivating) can cause red-eyed vireos to abandon the area for 20 to 30 years. If these activities must occur, efforts should be made to leave adequate canopy cover and find a balance between human resource use and environmental protection.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
There are no known adverse effects of Vireo olivaceus on humans.
To some extent, Vireo olivaceus controls insect pest populations through it's insectivorous diet. Red-eyed vireos provide little economic benefit to humans.
As primarily insectivores, Vireo olivaceus impact the insect populations they prey upon. Adults, young, and eggs may all be preyed upon and may support local predators. Red-eyed vireos also serve as hosts to parasites such as protozoan blood parasites, feather lice, mites, and hippoboscid flies. Red-eyed vireo nests are often parasitized by brown-headed cowbirds, usually resulting in nest failure. Vireos have on occasion buried the cowbird eggs and built a new nest over top, but this behavior is rare.
Commensal/Parasitic Species:
Vireo olivaceus is primarily an insectivorous species, but also occasionally eats fruit. Diet changes seasonally from nearly exclusively insects during the spring and summer to nearly all fruit during the winter. Main food sources include butterfly larvae (Lepidoptera), beetles (Coleoptera), mosquitoes (Diptera), cicadas (Homoptera), wasps and ants (Hymenoptera), grasshoppers (Orthoptera) and dragonflies (Odonata). These vireos also consume snails (Mollusca) and spiders (Arachnida), although rarely. Red-eyed vireos are foliage gleaners and capture insects setting on leaves or stems while perched, flying or hanging upside-down. There have been a few observations of red-eyed vireos drinking water that had collected on leaves.
Fruits and trees often utilized by red-eyed vireos include dewberries (Rubus), elderberries (Sambucus canadensis), Virginia creeper (Parthenosisus quinquefolia), sassafras (Sassafras albidum), spicebush (Lindera benzoin), dogwood (Cornus), northern arrowwood (Viburnum recognitum), northern bayberry (Myrica pensylvanica), and southern magnolia (Magnolia grandiflora).
Animal Foods: insects; terrestrial non-insect arthropods; mollusks
Plant Foods: fruit
Primary Diet: carnivore (Insectivore )
Vireo olivaceus is a migratory species that inhabits the Nearctic and Neotropical regions. During the non-breeding season, this species inhabits northeastern South America and is found east of the Andes Mountains as far south as Uruguay. In early spring, Vireo olivaceus travels north through southern Central America, along the Gulf coast and across Cuba, Haiti and the Dominican Republic. Vireo olivaceus breeds across nearly all of the United States, excluding the southwest region. Red-eyed vireos are rarely found south of Oregon or west of Colorado. Their breeding range extends as far north as the Northwest Territories and stretches from nearly coast to coast across southern Canada. Some Vireo olivaceus populations remain in South America to breed and move as far south as northern Argentina, but stay east of the Andes Mountains.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Vireo olivaceus prefers to breed in deciduous or mixed forest with dense canopy cover. In coniferous dominated stands they are most often found near riparian areas. They also breed in forested urban parks or cemeteries with old-growth trees that provide a dense canopy. They may be found anywhere from sea level to 2,000 m above in the Rocky Mountains.
In migration, Vireo olivaceus can be found in habitats similar to those used for breeding. They visit a slightly broader range of habitats during migration and may be found in forest edge, second growth forest, or citrus groves.
During the non-breeding season, red-eyed vireos prefer rain forests, second growth forests, plantations and forest edge habitats. They select habitats located from sea level to 3,000 m above.
These vireos are largely considered forest interior species but recent research is suggesting otherwise. Red-eyed vireos have been shown to select sites based on high levels of canopy cover and may be influenced very little by edge effect or fragmentation.
Range elevation: 0 to 3000 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: taiga ; forest ; rainforest
Other Habitat Features: urban ; riparian
The annual adult survivorship for Vireo olivaceus is estimated at 0.58. Survival rates for chicks post-fledging is much lower, estimated at 0.28. The oldest known red-eyed vireo was banded as an adult in 1963 and recaptured in 1972, making the individual at least 10 years old. Vireo olivaceus is not kept in captivity. Causes of mortality are poorly understood but likely include parasites, brood parasitism, predation, and stress of long-distance migration. Many birds do not survive migration and perish in collisions with buildings or other tall objects during night journeys.
Range lifespan
Status: wild: 10 (high) years.
Like all Vireo species, Vireo olivaceus is a small, perching songbird with relatively large, hooked bills. They measure 15.24 cm in length, feature a 25.4 cm wingspan, and weigh an average 18 g. Red-eyed vireos are recognized for their dark red irides that adults feature. However, this characteristic is rarely seen in the field as they are often at the tops of trees. They are olive-green across the nape, back, wings and tail. Throat, breast, and belly are bright white, while the under tail coverts and flanks are pale yellow. These vireos have a gray crown with a contrasting thick, white supercilium and a dark gray eye-line. Bills and legs are dark gray to black. Vireo olivaceus exhibits no sexual dimorphism and juveniles resemble adults, but are more gray-ish green overall.
Closely related species include Vireo flavoviridis and Vireo altiloquus. Their breeding ranges do not overlap, but they may overwinter in similar regions of South America. Vireo flavoviridis can be distinguished by brighter and more extensive yellow under tail coverts, flanks and cheeks. They also have a pale, larger bill as opposed to the dark smaller bill of Vireo olivaceus. Vireo altiloquus is overall brownish-green, with very pale yellow on the under tail coverts and flanks, as well as a defining black "whisker" or lateral stripe down the throat. Each of these species is best defined by song.
Average mass: 17 g.
Average length: 15.2 cm.
Average wingspan: 25.4 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Vireo olivaceus is a monogamous species, but the length of pair-bonds is currently unknown. Males arrive early at the breeding grounds to establish territory and pair formation occurs shortly after the females arrive. No courtship rituals have been observed, but males often chase potential mates and occasionally pin the females to the ground. Red-eyed vireos have been observed to perform a "swaying" display, but this is currently hypothesized to be used to appease individuals rather than court.
Mating System: monogamous
Males arrive on the breeding grounds from mid-March to early May and immediately establish territories. First year individuals are able to breed. Females arrive 3 to 15 days later and select a nesting site within a male's territory. Nests are generally constructed in the crook of a branch in the mid- to understory layer. The most successful nests are well concealed from above by foliage. Female red-eyed vireos build the cup-shaped nests using grasses, twigs, roots, bark strips, or spiderwebs. The females line their nests with softer materials such as grass, pine needles, and occasionally animal hair.
Once the nest is constructed, females lay an average clutch of 4 white, spotted eggs. Females perform all incubation which lasts between 11 and 14 days. After the young hatch, they are tended by both parents. The tiny hatchlings initially weigh between 1.5 and 1.8 g. The young fledge after 10 to 12 days and reach independence after an additional 25 days when the parents stop providing food.
Breeding interval: Red-eyed vireos breed once yearly.
Breeding season: The breeding season for red-eyed vireos occurs from mid-April to August.
Range eggs per season: 3 to 5.
Range time to hatching: 11 to 14 days.
Range fledging age: 10 to 12 days.
Range time to independence: 35 to 37 days.
Average age at sexual or reproductive maturity (female): <1 years.
Average age at sexual or reproductive maturity (male): <1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Male Vireo olivaceus invest time and energy in establishing suitable nesting territories. Males frequently engage in chases and physical aggression to defend their territories. Once females arrive, they provide the majority of parental care. Females select suitable nesting sites and complete all nest construction. Incubation and subsequent brooding of the young is also performed solely by the female. Hatchlings are altricial at birth, which requires significant parental care to feed, protect, and warm the defenseless young. Both parents actively consume or remove egg shells from the nest, which likely reduces the chance of predation by removing the scent of eggs. Fecal sacs are also removed by both parents, mostly by females, and are consumed until the 7th day post-hatch. Males contribute to feeding the hatchlings, but females provide the majority of food. Parents continue to feed the young frequently until 15 or 16 days post-fledging, but then drastically decrease feeding until 25 days post-fledge when feeding ceases.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
A large (6 inches) vireo, the Red-eyed Vireo is most easily identified by its olive-green back and tail, pale breast, plain wings, and deep red eyes with white eye-stripes. This species may be separated from the Philadelphia Vireo (Vireo philadelphicus), which also has a pale breast and plain back, by that species’ smaller size and yellower breast. Male and female Red-eyed Vireos are similar to one another in all seasons. The Red-eyed Vireo breeds across the eastern United States and southern Canada. This species also occurs in western Canada and parts of the Pacific Northwest, although it is less widespread in those portions of its range. This species is a long-distance migrant, spending the winter in northern and central South America. Red-eyed Vireos breed in a number of woodland habitats with dense undergrowth. During the winter, this species may be found in similarly-structured habitats in and around humid tropical forests. Red-eyed Vireos primarily eat small insects during the summer, but mostly switches to fruits and berries during the winter. In appropriate habitat, Red-eyed Vireos may be seen foraging for food on leaves and branches in the tree canopy as well as in the undergrowth. Birdwatchers may also listen for this species’ song, a series of fluty notes vaguely recalling portions of American Robin songs. Red-eyed Vireos are primarily active during the day, but, like many migratory songbirds, this species migrates at night.
A large (6 inches) vireo, the Red-eyed Vireo is most easily identified by its olive-green back and tail, pale breast, plain wings, and deep red eyes with white eye-stripes. This species may be separated from the Philadelphia Vireo (Vireo philadelphicus), which also has a pale breast and plain back, by that species’ smaller size and yellower breast. Male and female Red-eyed Vireos are similar to one another in all seasons. The Red-eyed Vireo breeds across the eastern United States and southern Canada. This species also occurs in western Canada and parts of the Pacific Northwest, although it is less widespread in those portions of its range. This species is a long-distance migrant, spending the winter in northern and central South America. Red-eyed Vireos breed in a number of woodland habitats with dense undergrowth. During the winter, this species may be found in similarly-structured habitats in and around humid tropical forests. Red-eyed Vireos primarily eat small insects during the summer, but mostly switches to fruits and berries during the winter. In appropriate habitat, Red-eyed Vireos may be seen foraging for food on leaves and branches in the tree canopy as well as in the undergrowth. Birdwatchers may also listen for this species’ song, a series of fluty notes vaguely recalling portions of American Robin songs. Red-eyed Vireos are primarily active during the day, but, like many migratory songbirds, this species migrates at night.
The red-eyed vireo (Vireo olivaceus) is a small American songbird. It is somewhat warbler-like but not closely related to the New World warblers (Parulidae). Common across its vast range, this species is not considered threatened by the IUCN.
"Vireo" is a Latin word referring to a green migratory bird, perhaps the female golden oriole, possibly the European greenfinch. The specific olivaceus is Neo-Latin for olive-green, from Latin oliva "olive".[2][3]
Adults are mainly olive-green on the upper parts with white underparts; they have a red iris and a grey crown edged with black. There is a dark blackish line through the eyes and a wide white stripe just above that line. They have thick blue-grey legs and a stout bill. They are yellowish on the flanks and undertail coverts (though this is faint in some populations).
In the past, the yellow-green vireo (V. flavoviridis), the chivi vireo (V. chivi), and the Noronha vireo (V. gracilirostris) have been considered to be conspecific with the red-eyed vireo; the chivi vireo was split most recently. Other closely related species include the black-whiskered vireo (V. altiloquus) and the Yucatan vireo (V. magister).
Measurements:[4]
Both sexes:
Red-eyed vireos are one of the most prolific singers in the bird world. They usually sing high up in trees for long periods of time in a question-and-answer rhythm. This species holds the record for most songs given in a single day among bird species, with more than 20,000 songs in one day.
Songs generally consist of 1-5 syllables between 2 and 6 kHz.[5] Songs are usually spaced apart by 0.8–1 seconds although at times vireos may sing at a slower or faster rate.[5] Red-eyed vireos have a large repertoire size with one study finding an average of 31.4 song types per bird with one individual singing 73 different song types.[5]
The breeding habitat of the red-eyed vireo is in the open wooded areas across Canada and the eastern and northwestern United States. These birds migrate to South America, where they spend the winter. The Latin American population occur in virtually any wooded habitat in their range. Most of these are residents, but the populations breeding in the far southern part of this species' range (e.g. most of its range in Argentina, Uruguay, Paraguay and Bolivia) migrate north as far as Central America.
In northern Ohio, it seems to return to breed at about the same time as one century ago; but it may leave for winter quarters one or two weeks earlier at present than it did in the past.[6]
Red-eyed vireos glean insects from tree foliage, favouring caterpillars and aphids and sometimes hovering while foraging. In some tropical regions, they are commonly seen to attend mixed-species feeding flocks, moving through the forest higher up in the trees than the bulk of such flocks.[7]
They also eat berries, especially before migration, and in the winter quarters, where trees bearing popular fruit like tamanqueiro (Alchornea glandulosa) or gumbo-limbo (Bursera simaruba) will even attract them to parks and gardens.[8] Fruit are typically not picked up from a hover, but the birds often quite acrobatically reach for them, even hanging upside down.[9]
The nest is a cup in a fork of a tree branch. The red-eyed vireo suffers from nest parasitism by the brown-headed cowbird (Molothrus ater) in the north of its range, and by the shiny cowbird (M. bonariensis) further south. Parasitism by Haemoproteus[10] and trypanosoma might affect these birds not infrequently, as was noted in studies of birds caught in Parque Nacional de La Macarena and near Turbo (Colombia): though only three red-eyed vireos were examined, all were infected with at least one of these parasites.[11]
The red-eyed vireo is a visitor to some western states, especially California.[12] This vireo is one of the more frequent American passerine vagrants to Europe, with more than one hundred records, mainly in Ireland and Great Britain.
The red-eyed vireo (Vireo olivaceus) is a small American songbird. It is somewhat warbler-like but not closely related to the New World warblers (Parulidae). Common across its vast range, this species is not considered threatened by the IUCN.
"Vireo" is a Latin word referring to a green migratory bird, perhaps the female golden oriole, possibly the European greenfinch. The specific olivaceus is Neo-Latin for olive-green, from Latin oliva "olive".
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