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Photo by Cornell Laboratory of Ornithology.
This species was on the 2002 WatchList, but is not on the 2007 WatchList. Please refer to http://web1.audubon.org/science/species/watchlist/techReport.php for information on the 2007 WatchList.
Found mainly in the large deciduous forests of Appalachia and neighboring states, the Worm-eating Warbler is a rather inconspicuous ground-nesting warbler that prefers steep hillsides. Forest fragmentation on its breeding grounds increases the bird's exposure to nest predation and cowbird parasitism, while deforestation of broadleaf forest on the species' wintering grounds in the Caribbean and Central America could also lead to population declines.
Although rather modestly colored when compared with other wood warblers, this species is easily identified by its striking head pattern of alternating black and buff stripes. The buffy coloration of the face extends down onto the breast, before fading to a whitish color on the lower belly. The upperparts of Worm-eating Warbler are a drab olive.
The heart of Worm-eating Warbler's breeding range stretches from northern Alabama and Georgia northward through the Appalachian states to southern New York and Connecticut. This species can also be found breeding westward to Louisiana, Arkansas, and Missouri. A number of Audubon Important Bird Areas (IBAs) support breeding populations of Worm-eating Warbler, including New York's Sterling Forest IBA and Fahnestock State Park and Hubbard/Perkins Conservation Area IBA, Pennsylvania's Kittatinny Ridge IBA and Susquehanna Riverlands IBA, and North Carolina's Blue Ridge Escarpment Gorges IBA. This species winters from southern and eastern Mexico south to Panama, and also in the West Indies, Bahamas, Greater Antilles, and Virgin Islands.
Small sample sizes from the Breeding Bird Survey (BBS) make it difficult to determine population trends for this species. BBS data from 1966 to 2000 indicate a non-significant increase of 0.75% per year for Worm-eating Warbler across its entire range. However, in areas where this species is most abundant, such as West Virginia, Tennessee, and the Ohio Hills, analysis of BBS data shows a decline, although most of this decline is from before 1980.
The Worm-eating Warbler nests on the ground in leaf litter, on a steep slope or hillside or along a ravine, in deciduous or mixed woodlands with dense understory. It typically breeds in a region with a combination of oak, beech, maple, hickory, chestnut, magnolia, hemlock, and pine. The female builds a cup nest in which she typically lays four or five eggs; she then incubates the eggs for about 13 days. The young, fed by both parents, leave the nest about 10 days after hatching.
Despite its name, Worm-eating Warbler only rarely, if ever, eats earthworms. Instead, it feeds mostly on caterpillars (once referred to as "worms"), other insects, spiders, and slugs. An interesting habit of this bird is its penchant for foraging in dead leaves hanging from trees. Some data suggest that the bird chooses chestnut oaks for feeding early in the breeding season, and then switches to understory shrubs in July.
Worm-eating Warblers start departing from their breeding grounds in late July, and arrive on their wintering grounds by October. They return to their breeding grounds earlier than some warblers, with the first migrants arriving on the Gulf Coast by late March and more northern breeders in the Northeast arriving back on territory in late April or early May.
Tropical deforestation on wintering grounds and forest fragmentation on breeding grounds are the main threats facing Worm-eating Warbler. This species' dependence on tropical broadleaf forest during the winter makes it "highly vulnerable" to future population decline. As forest fragmentation on the bird's breeding ground increases, the Worm-eating Warbler becomes more susceptible to Brown-headed Cowbird parasitism and nest predation.
Audubon Pennsylvania recently launched the Kittatinny Ridge Conservation Project, a two-year comprehensive planning and public involvement process to conserve the 180,000-acre Kittatinny Ridge IBA-the state's largest IBA providing habitat for large numbers of Worm-eating Warblers and other birds. Audubon South Carolina added more than 180-acres of habitat to the Beidler Forest Reserve in 2001 protecting habitat for Worm-eating Warblers and other species.
Worm-eating Warbler has been identified as a priority species in a number of Partners in Flight physiographic areas, including the Ohio Hills, Mid-Atlantic Ridge and Valley, and Northern Ridge and Valley areas. The objective of the Mid-Atlantic Ridge and Valley planning area includes preserving 120,000 hectares of mature deciduous forest, which should be able to support 50,000 pairs of Worm-eating Warbler. The objective of the Northern Ridge and Valley physiographic area includes providing 40,000 hectares of suitable habitat for 18,000 pairs of Worm-eating Warbler.
What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Worm-eating 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/.
Audubon and our partners in conservation coordinated the submission of over two million comments to the U.S. Forest Service in support of the Roadless Area Conservation Rule, which would protect habitat for Worm-eating Warbler and many other species. Unfortunately, implementation of the Rule has been stalled and attempts are being made to weaken it. To help in protecting these vital habitats visit: http://www.audubon.org/campaign/latestnews.html#roadless.
The Cornell Laboratory of Ornithology and the USDA Forest Service coordinate Birds in Forested Landscapes, a citizen-science project that links volunteer birders and professional ornithologists in a study of the habitat requirements of North American forest birds, including Worm-eating Warbler. To learn more about Birds in Forested Landscapes, and how you can participate in the project, visit: http://birds.cornell.edu/bfl/.
Dunn, J., and K. Garrett. 1997. Peterson Field Guide: Warblers. Houghton Mifflin Company, New York.
Hanners, L.A., and S.R. Patton. 1998. Worm-eating Warbler (Helmitheros vermivorus). In The Birds of North America, No. 367 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.
Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.