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Photo by Ohio Dept. of Natural Resources.
This canopy foraging insectivore breeds in mature and older deciduous forests with broken canopies in the eastern U.S. It migrates farther and earlier, and forages and nests higher in the canopy than many other warbler species. Formerly one of the most abundant breeding warblers in Ohio and the Mississippi River Valleys, its population plummeted in the 1900's due to habitat destruction.
This wood-warbler is not easily confused with other warblers. The adult male is a deep cerulean blue above with a streaked back, and is white below with a narrow blue-black band across the throat. The adult female is bluish-green above with no streaks, and white washed with yellow below with a distinct white or yellowish line over eye. All plumages and both sexes have white wing bars and white tail-spots.
The species suffers from habitat loss and degradation in both its summer and winter range. The remaining population breeds in the northeastern and central parts of the United States as far north as s. Ontario, as far south as Arkansas, as far east as the Atlantic Coast, and as far west as Iowa. Ceruleans are not evenly distributed throughout this range. Historically, they were especially abundant in the old-growth bottomland forests of the Mississippi Alluvial Valley, but these forests no longer exist. Mesic upland forests are scarce now as well. The species winters in the canopies and borders of broad-leaved, evergreen forests and woodland at middle to lower elevations on the eastern and western slopes of the Andes and montane forests of northern South America. Here the land is being cultivated for growing coca. Ceruleans have shown one of the steepest declines of any warbler species, showing a decline of -4.5% per year from 1966-2001 according to the Breeding Bird Survey.
Typically found in mature forested areas with large and tall trees of broad-leaved, deciduous species and an open understory, but may also inhabit wet bottomlands, some second-growth forests, and mesic upland slopes. Eats insects in the foliage and a small amount of plant material in the winter. Nests high in the canopy on a lateral limb of a deciduous tree above an open area. The nest is concealed from above by leaves or vines. The 3-4 eggs are incubated by the female, but both parents feed the young. As a medium- to long-distance migrant, these warblers may arrive on their breeding range from late March to mid-May and be back on their wintering grounds as early as August.
The main threat is from habitat degradation and forest fragmentation as the human population increases and land-uses change. Breeding habitat is degraded when mature deciduous forests, especially riparian forests, are lost; remaining forests are fragmented and isolated; less deciduous forests reach maturity because of shorter rotation periods and even-aged management; key tree species are lost because of disease. Winter habitat is being destroyed for the production of coffee beans and coca as the demand for coffee and illegal cocaine-based drugs grows.
Current conservation projects include habitat acquisition and protection, which considers the minimum amount of land necessary to support the Cerulean Warbler; land acquisition and protection by various agencies and local land trusts; and the Cerulean Warbler Atlas Project by the Cornell Lab of Ornithology that seeks to learn more about where Ceruleans are and their habitat needs. Land management that supports Ceruleans would involve maintaining forests with distinct canopy layers. Because the Cerulean is also an area-sensitive species, meaning that it requires a large tract of suitable forest cover, management at the landscape level also needs to be considered. Ideally, large tracts of suitable habitat should be self-sustaining.
What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Cerulean Warblers 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/.
U.S. National Wildlife Refuges provide essential habitat for Cerulean Warblers, 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 Cerulean 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.
BirdLife International (2006) Species factsheet: Dendroica cerulea, Cerulean Warbler http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=9120&m=0
Hamel, P. B. 2000. Cerulean Warbler (Dendroica cerulea). In The Birds of North America, No. 511 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.