This small, canopy-foraging insectivore breeds locally in mature and older deciduous forests with broken canopies across much of the eastern United States. Sky blue, sky high in the canopy, the Cerulean Warbler has been little studied; management actions to enhance its habitat have not yet been specified. Among Dendroica, this species forages and nests higher in the canopy, and migrates farther and earlier, than most others. Its social system remains poorly understood. Numerous interesting questions about wintering individuals in montane South American forests, where this species associates with others in mixed flocks of canopy insectivores, await investigation.
Although the Cerulean Warbler was formerly among the most abundant breeding warblers in the Ohio and Mississippi River valleys, its numbers plummeted in the 1900s. Concern for the future of this species is warranted. Yet even in the face of these steep declines, some populations are currently expanding.
Several independent teams have investigated this warbler on its breeding grounds: in southern Illinois, by the Illinois Natural History Survey, principally Scott Robinson (Vanderah and Robinson 1995); in the Cumberland Plateau, by the University of Tennessee (Knoxville), principally David Buehler and Charles Nicholson (Nicholson and Buehler 1998); southern Ontario, by scientists at Queen's University, principally Raleigh Robertson (Oliarnyk 1996; Oliarnyk and Robertson 1996; Jones and Robertson 1997, 1998); and in the lower Mississippi Alluvial Valley, by scientists at the USDA Forest Service, Southern Hardwoods Lab, principally the author. Progress reports on the work of these groups were combined in a 1998 symposium (Hamel 1998a).
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