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Kentucky Warbler
Geothlypis formosa
– Family
Authors: McDonald, Mary Victoria
Revisors: McDonald, Mary Victoria

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Adult male Kentucky Warbler, Marblehead, MA, 11 May.
Figure 1. Distribution of the Kentucky Warbler.

The song of the Kentucky Warbler is a familiar sound of rich, moist, deciduous forests in the southeastern United States. A skulking, ground-nesting bird, this warbler is heard more often than seen. In early spring, the male sings incessantly, sometimes partly concealed and almost motionless except for his vibrating throat, in bouts from the same perch for 5–15 minutes, typically at heights of 5–15 meters. Although his song may be confused with that of the Carolina Wren (Thryothorus ludovicianus), or even the Ovenbird (Seiurus aurocapilla), a flash of yellow and black when he changes perches confirms the Kentucky Warbler.

Numbers of this species appear to be declining, more in some regions than in others. Tropical deforestation may be one factor affecting this species. Data from several key studies (e.g., in Virginia and Arkansas) have provided a fairly good overview of the mating, territorial, and nesting behavior of this species, as well as annual survival of marked birds and early arrival and late departure dates from a long-term study in Virginia (MVM). Breeding-season distributional data, especially from Breeding Bird Atlas projects, notes published in state journals, and unpublished information are also fairly comprehensive.

As with most species, however, little is known about the postbreeding dispersal of juveniles and fall migration. Many studies of Neotropical migrants in Mexico and Central America include migrant or wintering Kentucky Warblers in their data sets, and at least 1 attempt (Mabey 1991) has been made to study a small banded population through 2 seasons in Panama. Much more research is needed on the migration and wintering ecology of the Kentucky Warbler.