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Photo by Chandler Robbins.
A bird of shrubby second-growth habitat on its northeastern U.S. breeding grounds, the Blue-winged Warbler, like many shrubland bird species, is showing population declines across its range. The species is also hybridizing with and replacing Golden-winged Warblers in much of the eastern U.S.
Adult male in all plumages has a bright yellow head and underparts, a greenish-yellow back and nape, a blue-gray wing and tail, and a black eye line. Another distinguishing feature of this 4.75-inch long bird is two white wing bars, often tinged with yellow. Females are similar, but paler overall.
The Blue-winged Warbler hybridizes with the Golden-winged Warbler. Two basic hybrid types occur - the Brewster's Warbler with yellow head and throat, white belly, and white wing bars and the Lawrence's Warbler (less common) with a yellow crown and belly; black throat and eye patch; and whitish wingbars.
During the late 1800s, Blue-winged Warblers began expanding their breeding range northward from the Ozark Mountains and wooded savannas of Tennessee and Kentucky, perhaps in response to landscape changes, i.e. clear-cutting forests. Regrowth of forests, coupled with loss of habitat to development, has caused a decline in this species in the northeastern United States. Today the Blue-winged Warbler breeds in the eastern United States from southeastern Minnesota and southern Ontario south to Missouri, Arkansas, and Tennessee. It shuns heavy agricultural areas, for example, the corn and soybean desert of central Illinois. Blue-winged Warblers occur as breeders on a number of Audubon Important Bird Areas including New York's Hi-Tor Wildlife Management Area IBA, Long Island Pine Barrens IBA, and Connecticut's Bent of the River Audubon Center IBA. The Blue-winged Warbler winters along the Atlantic slope of Mexico and Central Mexico where it prefers humid evergreen and semi-deciduous forests at low and middle elevations. The Breeding Bird Survey shows a 0.7% annual decline across the species range from 1966-2001.
The Blue-winged Warbler chooses forest-field regions that are often shaded by large trees. The female places a nest on or near the ground at the base of berry bushes, goldenrods and other shrubby plants and forbs. In May and June, she builds a round, sprawling, narrow, deep basket of dead leaves, grasses, and bark shreds. Incubation lasts 11 to 12 days; the young fledge in about ten days - leaving the nest within one hour of each other over a day or two. Brown-headed Cowbirds parasitize this species, reducing its reproductive success.
The Blue-winged Warbler hybridizes with the Golden-winged Warbler where the breeding ranges overlap; ornithologists are trying to piece together the puzzle of how this hybridization is affecting populations of both species. Although the bird's food choices have been poorly documented, it probably eats mostly beetles, moths, moth larvae, flies, bugs, grasshoppers, crickets, and spiders. The Blue-winged Warbler departs in July to return to its wintering grounds; it is an early-arriving warbler in spring, entering the United States in late March.
Suburban expansion of the human population is depleting habitat for this species. For example, nine former breeding sites in northeastern Ohio have been converted to housing developments; Blue-winged Warblers no longer breed there. Tropical deforestation to make way for coffee plantations and other monoculture-type crops may be reducing the species' winter range. Conservation concerns are highest in the states of Connecticut, New Jersey, Ohio, Kentucky, and Alabama.
As awareness continues to increase towards managing for the needs of species inhabiting shrubby, early successional habitats, public and private land managers have begun using a variety of management tools including prescribed burns in fire-dependent habitats, mechanical removal of vegetation to mimic disturbance, and other activities. Audubon Connecticut's Bent of the River Center actively manages its shrub habitats in this way to maintain a breeding population Blue-winged Warblers. Many scrub oak-pine barren ecosystems in the eastern U.S., which sometimes support populations of Blue-winged Warblers, have been the focus of intensive protection efforts. In these areas, much land has been purchased and often regulations have been implemented to reduce the impacts of development. Prescribed burns continue to be an actively used tool in these fire-evolved ecosystems.
What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Blue-winged Warbler as well as other species. To learn more about the Important Bird Areas program and how you can help, visit: http://www.audubon.org/bird/iba/.
Support local land trusts, government agencies, and other organizations working to preserve shrub habitats in your area. Contact your state Important Bird Areas coordinator (http://www.audubon.org/bird/iba/state_coords.html) to find out if there are sites in your area important for Blue-winged Warblers that need increased protection.
U.S. National Wildlife Refuges provide essential habitat for Blue-winged Warbler, and a great number of other species throughout the U.S. and its territories. Unfortunately, the refuge system is often under-funded during the U.S. government's budgeting process. To learn more about how you can help gain much needed funding for U.S. National Wildlife Refuges, visit: http://www.audubon.org/campaign/refuge_report/
Information on where Blue-winged Warblers occur and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab of Ornithology, eBird is the world's first comprehensive on-line bird monitoring program: http://www.audubon.org/bird/ebird/index.html.
Much more needs to be known about this species' preferred habitats and its interaction with the Golden-winged Warbler, with whom it hybridizes. The Golden-winged Warbler, which also breeds in shrubby habitats, is considered to be more threatened than the Blue-winged. To participate see the Cornell Lab of Ornithology's Golden-winged Warbler Atlas Project web site at http://birds.cornell.edu/gowap/
Purchase shade-grown coffee to help conserve the Blue-winged Warbler and other neotropical migrants. Seattle Audubon has implemented a Northwest Shade Coffee Campaign with excellent information at their website: http://www.seattleaudubon.org/Coffee/home.html.
Dunn, J. and K. Garrett. 1997. Peterson Field Guide: Warblers. Houghton Miffllin. New York.
Gill, F.B., R.A. Canterbury, and J.L. Confer. 2001. Blue-winged Warbler (Vermivora pinus). In The Birds of North America, No. 584 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.