Source: https://birdsna.org/Species-Account/bna/species/reevir1/introduction
Timestamp: 2019-04-21 10:38:38+00:00

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Large vireo with a gray to blue-gray crown that contrasts with plain, grayish olive-green upperparts and rather prominent whitish supercilium. Lateral edges of crown bordering supercilium above form sharp blackish line; dusky eyeline extends from lores to behind eye, where it gradually becomes less distinct. Underparts white, tinged pale yellow when fresh. Iris bright red to crimson, rarely brownish red. The brown primary coverts, the narrow pointed rectrices, and the lack of contrast between the tertials and the secondaries indicate that this is a bird in Formative Plumage. Eye color also still is not quite fully red.
One of the most common breeding songbirds in the woodlands of eastern North America, the Red-eyed Vireo is more often heard than seen. This species' persistent song is heard throughout the day: cherr-o-wit, cheree, sissy-a-wit, tee-oo. Indeed, the unending and monotonous character of its song prompted Bradford Torrey in 1889 to reflect wryly, “I have always thought that whoever dubbed this vireo the ‘preacher' could have had no very exalted opinion of the clergy” ( Tyler, W. M. (1950b). "Vireo olivaceus (Linnaeus) Red-eyed Vireo." In Life histories of North American wagtails, shrikes, vireos, and their allies., edited by A. C. Bent, 335-348. U.S. Natl. Mus. Bull. 197.
As with many Nearctic–Neotropical migrants, the evolutionary origin of the Red-eyed Vireo can likely be traced to the Neotropics ( Cicero, C. and N. K. Johnson. (1998). Molecular phylogeny and ecological diversification in a clade of New World songbirds (genus Vireo). Molecular Ecology 7 (10):1359-1370.
2). This species overwinters principally in the Amazon basin of South America east of the Andes and breeds extensively in eastern North America and west across Canada and the northern United States. The sexes are weakly dimorphic and socially monogamous. The female builds the nest, incubates eggs, and devotes more time than the male to brooding and feeding of young. This species is largely insectivorous during the breeding season, when they are most often observed foraging in canopy vegetation. During the nonbreeding season, fruit is an important part of the diet, especially in migration and tropical overwintering habitats. A mixed diet of fruit and insects is especially conducive to fat deposition during migration. The Red-eyed Vireo is a nocturnal migrant whose magnetic compass figures prominently in its orientation during intercontinental flight (R. Sandberg, J. Bäckman, M. Lohmus, personal communication).
The Red-eyed Vireo is part of the subgenus Vireosylva and the larger Vireo olivaceus superspecies complex, which includes Yellow-green Vireo (V. flavoviridis) of Middle America, Black-whiskered Vireo (V. altiloquus) of southern Florida and the West Indies, Yucatan Vireo (V. magister) of Yucatan Peninsula and nearby islands, Chivi Vireo (V. chivi) of tropical lowland South America, and Noronha Vireo (V. gracilirostris) of Fernando de Noronha, Brazil. Evolutionary relationships within this complex have challenged taxonomists for decades. For example, V. flavoviridis and V. altiloquus were lumped into V. olivaceus for many years, but eventually were generally treated as species. Despite those splits, V. chivi continued to be lumped with V. olivaceus until phylogenetic analyses revealed paraphyly between the North American and South American lineages of V. olivaceus with respect to V. altiloquus ( Slager, D. L., C. J. Battey, R. W. Bryson, Jr., G. Voelker, and J. Klicka (2014). A multilocus phylogeny of a major New World avian radiation: The Vireonidae. Molecular Phylogenetics and Evolution 80:95–104.
3, Battey, C. J., and J. Klicka (2017). Cryptic speciation and gene flow in a migratory songbird species complex: Insights from the Red-eyed Vireo (Vireo olivaceus). Molecular Phylogenetics and Evolution 113:67-75. doi: 10.1016/j.ympev.2017.05.006.
4), leading to the recent taxonomic split of V. olivaceus and V. chivi ( Chesser, R. T., K. J. Burns, C. Cicero, J. L. Dunn, A. W. Kratter, I. J. Lovette, P. C. Rasmussen, J. V. Remsen, Jr., D. F. Stotz, B. M. Winger, and K. Winker (2018). Fifty-ninth supplement to the American Ornithological Society's Check-list of North American Birds. Auk 135 (3):798-813.
Important information is available on communication ( Lemon, R. E. (1971). Analysis of song of Red-eyed Vireos. Can. J. Zool. 49:847-854.
6, Barlow, J. C. and J. C. Rice. (1977). Aspects of the comparative behavior of Red-eyed and Philadelphia vireos. Can. J. Zool. 55:528-541.
7, Borror, D. J. (1981). The songs and singing behavior of the Red-eyed Vireo. Condor 83:217-228.
8), breeding biology ( Lawrence, L. K. (1953a). Nesting life and behaviour of the Red-eyed Vireo. Can. Field Nat. 67:47-77.
9, Southern, W. E. (1958). Nesting of the Red-eyed Vireo in the Douglas Lake region, Michigan. Jack-Pine Warbler 36:105-130.
10, Barlow, J. C. and J. C. Rice. (1977). Aspects of the comparative behavior of Red-eyed and Philadelphia vireos. Can. J. Zool. 55:528-541.
7), foraging behavior ( James, R. D. (1976a). Foraging behavior and habitat selection of three species of vireos in southern Ontario. Wilson Bulletin 88:62-75.
11, Robinson, S. K. and R. T. Holmes. (1982). Foraging behavior of forest birds: the relationships among search tactics, diet, and habitat structure. Ecology 63:1918-1931.
12), and migration ( Loria, D. E. and F. R. Moore. (1990). Energy demands of migration on Red-eyed Vireos (Vireo olivaceus). Behav. Ecol. 1:24-35.
13, Sandberg, R. and F. R. Moore. (1996). Migratory orientation of Red-eyed Vireos, Vireo olivaceus, in relation to energetic condition and ecological context. Behav. Ecol. Sociobiol. 39:1-10.

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