Black-whiskered Vireo Vireo altiloquus Scientific name definitions

This vocal yet sometimes elusive vireo, which breeds throughout the Caribbean Basin, is limited in the United States to coastal mangroves and hardwood forests of southern Florida. It resembles the closely related Red-eyed (Vireo olivaceus) and Yellow-green (V. flavoviridis) vireos in plumage, but can be distinguished from these by its black lateral throat stripe (so-called "whiskers") and browner back. Usually heard before the bird is seen, the song of this species is similar to that of the Red-eyed Vireo, but is sharper, with more abrupt pitch changes. A deliberate forager, the Black-whiskered Vireo gleans fruits and insects from the distal branches of trees and bushes, and occasionally hovers to obtain fruits. Its drab, greenish plumage and deliberate movement make it a difficult bird to observe in dense foliage.

In Florida, the Black-whiskered Vireo is generally a mangrove specialist, but throughout its extensive Caribbean range it prefers subtropical dry limestone and mesic lowland forests to mangroves. Northern populations (e.g., breeders in Florida and the Bahama Islands) are migratory, overwintering in lowland forests of the northern Amazon Basin. Farther south, a few are year-round residents in Hispaniola, Puerto Rico, and several other northern Caribbean islands, while in the southern part of its range most are permanent residents. Migratory Black-whiskered Vireos return to Florida, the Bahamas, and Greater Antilles to breed in early spring. Females build a pendant cup in a forked branch of an understory tree or tall shrub. Outside of Florida, nests are frequently built higher in subtropical and tropical evergreen forests.

Where this species coexists with the Shiny Cowbird (Molothrus bonariensis), the frequency of parasitism is usually high (> 50%) and causes significant reduction in reproductive output.

Black-whiskered Vireos that remain in the Greater Antilles during the nonbreeding season move to lower elevations, and must compete for food resources with overwintering warblers. Apparently, this species partitions its foraging niche through diet and foraging location. Black-whiskered Vireos consume nearly an equal amount of fruits and insects, and they forage higher in the canopy than most other gleaning insectivores during the overwintering period.

Across its breeding range in the Caribbean, the Black-whiskered Vireo is either the only vireo on an island, or it coexists with one other vireo species. Only on Jamaica does it breed sympatrically with two endemic vireos. Under these potentially competitive situations, the Black-whiskered has broader habitat tolerances, forages higher in the canopy, and consumes more fruit and larger insects than the island endemics. Interestingly, where Black-whiskered Vireos are permanent residents in the Lesser Antilles they are the only vireo on the island, and those islands occur beyond the southern extent of where many migrant warblers overwinter in the Caribbean.

This widespread Caribbean songster has been the focus of a number of avian-community studies. Habitat selection has been analyzed in Florida (Robertson 1955 Robertson, W. B., Jr. (1955). An analysis of the breeding bird populations of tropical Florida in relation to the vegetation. Ph.d. dissertation, University of Illinois, Urbana, IL, USA. Close ), Grand Bahama (Emlen 1977 Emlen, J. T. (1977) Land bird communities of Grand Bahama Island: the structure and dynamics of an avifauna. Ornithological Monographs 24. Close ), Puerto Rico (Wiley 1988 Wiley, J. W. (1988). Host selection by the Shiny Cowbird. Condor 90: 289–303. Close ), Jamaica (Lack 1976 Lack, D. (1976). Island Biology, Illustrated by the Land Birds of Jamaica. Volume 3. University of California Press, Berkeley, CA. USA. Close , Cruz 1980b Cruz, A. (1980b). Feeding ecology of the Black-whiskered Vireo and associated foliage-gleaning birds in Jamaica. Wilson Bulletin 92:40-52. Close ), Cayman Islands (Johnston 1975a Johnston, D. W. (1975). Ecological analysis of the Cayman Island avifauna. Bulletin of the Florida State Museum Biological Sciences 19:235–295. Close ), and the Lesser Antilles (Lack 1976 Lack, D. (1976). Island Biology, Illustrated by the Land Birds of Jamaica. Volume 3. University of California Press, Berkeley, CA. USA. Close ). Foraging ecology has been examined in a number of studies (Lack 1976 Lack, D. (1976). Island Biology, Illustrated by the Land Birds of Jamaica. Volume 3. University of California Press, Berkeley, CA. USA. Close , Cruz 1980a Cruz, A. (1980a) Avian feeding assemblages in Puerto Rico. Caribbean Journal of Science 15: 21–27. Close , Cruz 1987 Cruz, A. (1987) Avian community organization in a mahogany plantation on a neotropical island. Caribbean Journal of Science 23: 286–297. Close , Carlo 1999 Carlo, T. A. (1999). Diet, fruit preference and seed dispersal capabilities of fruit-eating birds in north central Puerto Rico. M.S. thesis, North Carolina State University, Raleigh, NC, USA. Close ), especially in relation to niche-partitioning among overwintering vireos (Barlow 1980b Barlow, J. C. (1980). Patterns of Ecological Interactions Among Migrant and Resident Vireos on the Wintering Grounds. In Migrant Birds in the Neotropics: Ecology, Behavior, Distribution, and Conservation (A. Keast and E. S. Morton, Editors). Smithsonian Institution Press, Washington, DC, USA. pp. 79–107. Close ), and with overwintering warblers in Puerto Rico (Terborgh and Faaborg 1980 Terborgh, J. W. and J. R. Faaborg (1980). Factors affecting the distribution and abundance of North American migrants in the eastern Caribbean region. In Migrant Birds in the Neotropics: Ecology, Behavior, Distribution, and Conservation (A. Keast and E. S. Morton, Editors), Smithsonian Institution Press, Washington, D.C., USA. pp. 145–155. Close ). As Black-whiskered Vireo is a host of Shiny Cowbird, brood parasitism has been studied in Puerto Rico (Wiley 1985a Wiley, J. W. (1985). Shiny Cowbird parasitism in two avian communities in Puerto Rico. Condor 87:165–176. Close , Pérez-Rivera 1986 Pérez-Rivera, R. A. (1986). Parasitism by the Shiny Cowbird in the interior parts of Puerto Rico. Journal of Field Ornithology 57:99–104. Close , Nakamura 1995 Nakamura, T. K. (1995). A test of the nest defense paradigm: are aggressive birds less parasitized? M.S. thesis, University of Colorado, Boulder, CO, USA. Close , BLW), the Dominican Republic (Cruz et al. 1989 Cruz, A., J. W. Wiley, T. K. Nakamura and W. Post. (1989). "The Shiny Cowbird Molothrus bonariensis in the West Indian region-biogeography and ecological implications." In Biogeography of the West Indies., edited by C. A. Wood, 519-540. Gainesville, FL: Sandhill Crane Press. Close ), and St. Lucia (Post et al. 1990 Post, W., T. K. Nakamura and A. Cruz. (1990). Patterns of Shiny Cowbird parasitism in St. Lucia and southwestern Puerto Rico. Condor 92:461-469. Close ) Aspects of the intriguing partial migratory status of this vireo have been illuminated by feather-chemistry analysis (Barlow and Bortolotti 1988 Barlow, J. C. and G. R. Bortolotti. (1988). Adaptive divergence in morphology and behavior in some New World island birds, with special reference to Vireo altiloquus. Acta XIX Congr. Int. Ornithol:1535-1549. Close ). Clearly, more study is needed in areas of life-history characteristics (outside of Puerto Rico and Jamaica), partially migratory subspecies, and the impacts of range expansion of Shiny Cowbird and Brown-headed Cowbird (M. ater) into Florida.