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Status: Population size: 1.1 million Photo by Glen Tepke.

Kentucky Warbler
(Oporornis formosus)

A characteristic breeding bird of the rich deciduous forests of southeastern United States, the Kentucky Warbler winters in Mexico, Central America, and northern South America. Although a rather handsome-looking bird, it is secretive and more often heard than seen.

Identification
The Kentucky Warbler is a shy, ground-dwelling bird with bright yellow underparts, olive upperparts, and, its most distinctive feature, a black mask and yellow "goggles." Adult females are similar, but lack the male's dark head markings. Plumages are similar year-round. The Kentucky Warbler's loud repeated two-syllable song resonates in the bottomland forests where it is more often heard than seen.

Distribution and Population Trends
The northern limit of the Kentucky Warbler's breeding distribution extends from New Jersey and Pennsylvania west to southern Wisconsin and southern Iowa. Its southern breeding limit is from South Carolina west to eastern Texas. This species' breeding range appears to have expanded slowly northward during the 20th century; though this may be a reoccupation of its former historic range. Audubon Important Bird Areas (IBA) that support breeding populations of the species include Maryland's Mattawoman Creek Natural Environment Area IBA, North Carolina's Roanoke River Bottomlands IBA, and Mississippi's Pascagoula River Wildlife Management Area IBA. The Kentucky Warbler winters from Mexico south through Central America to Panama with individuals rarely occurring to northern Colombia and Venezuela. Breeding Bird Survey data show a statistically significant 1% per year decline between 1966-2001 across its entire U.S. range.

Ecology
Southeastern bottomland hardwood forest with thick understory is the Kentucky Warbler's preferred nesting habitat. Within this habitat it frequently skulks, stealthily hopping or briefly running on the ground among leaf litter or on fallen logs. In May or June the female builds her well-concealed open cup nest with coarse grasses and oak leaves in dense understory just above the ground often on a slope. She typically anchors the nest to a small shrub. Nesting locations are often in deep, deciduous, moist woodlands with well-developed ground cover. Incubation lasts 11 to 13 days; young fledge from 7 to 10 days. The female sometimes gives distraction displays when the nest is disturbed. The Kentucky Warbler diet consists of insects, caterpillars, and small spiders during the breeding season. In Mexico during winter it may feed on cecropia fruits. The species leaves its breeding grounds in August to migrate, then returns again beginning in March. It is one of the earlier warblers to arrive back into North America for nesting.

Threats
On the breeding grounds the species has been hard-hit by losses of bottomland hardwood forests in the southeastern U.S., first for timber and later for conversion to agriculture. Some of the same habitats that once may have harbored the presumed-extinct Ivory-billed Woodpecker were also important breeding grounds for Kentucky Warblers though the latter species fortunately was not as habitat specialized and had a larger, more northerly range. In modern times, a major threat to the species habitat in many areas (along with the ever-present loss of habitat to development) is the often complete loss of understory vegetation across broad areas caused by browsing by an over-abundant White-tailed Deer population.

Conservation
Audubon Pennsylvania has taken a lead in working to find solutions to the habitat degradation caused by deer overpopulation in that state including hosting a conference to explore and understand the issue. For more information visit: http://www.audubon.org/chapter/pa/pa/deerintropage.htm. Audubon Mississippi is a lead organization in raising awareness to protect Kentucky Warbler habitat along the Pascagoula River IBA. See http://www.audubon.org/bird/iba/ms.html for more information.

The Kentucky Warbler Project at the Smithsonian Conservation and Research Center, is a long-term behavioral ecology research program to help conserve this neotropical migrant. Researchers are monitoring reproductive success and annual return rates; recording behavioral data; and interpreting numbers, trends, and changing distribution of Kentucky Warblers in relation to the rapidly changing and decreasing forest tracts in the Front Royal, Virginia area. For more information, see http://www.si.edu/crc/rp/rp_nature/rp_eco/m_birds/kew.htm

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Kentucky 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 bottomland hardwood forests 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 Kentucky Warblers that need increased protection.

U.S. National Wildlife Refuges provide essential habitat for Kentucky 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 Kentucky 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.

Purchase shade-grown coffee to help conserve the Kentucky 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. Atlanta Audubon also has an excellent website devoted to the topic at http://www.atlantaaudubon.org/pages/sgcfacts.htm.

References
Dunn, J. and K. Garrett. 1997. Peterson Field Guide: Warblers. Houghton Miffllin. New York.

McDonald, M.V. 1998. Kentucky Warbler (Oporornis formosus). In The Birds of North America, No. 324 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.