Introduction

The Hooded Warbler is a small migratory songbird that breeds in southernmost Canada and the eastern United States and winters in Central America. On its breeding range, this species inhabits mixed hardwood forests in the north and cypress-gum swamps in the south. Considered a forest-interior species because it is restricted to larger woodlots, the Hooded Warbler is declining in only a few parts of its breeding range, but is considered threatened in Canada where suitable habitat is becoming increasingly scarce and fragmented. Overwintering individuals are strongly territorial and segregate by sex, with males most likely to be found in mature forest and females in scrub, secondary forest, and disturbed habitats—the first documented case of such habitat segregation. Many individuals appear unable to obtain winter territories owing to this intense intraspecific competition, and little is known about the ecological or conservation implications of such behavior.

As with wintering ecology, song has been particularly well studied in this species. Males have individually distinctive songs and are known to associate each neighbor’s song with its usual location, a form of individual recognition. Long-term memory enables males to remember their individual neighbor’s songs from year to year, presumably reducing the costs of territorial defense.

Males defend nesting and feeding territories where they attract a single mate. A key feature of this species’ social behavior is extra-pair matings. DNA fingerprinting studies have revealed that about one-third of the females produce offspring fathered by a neighboring male. Such a mating system is typical of most long-distance migratory passerines and may have implications for habitat selection if individuals avoid small woodlots where there are few opportunities for extra-pair matings with conspecifics.

Adult male Hooded Warblers have distinctive plumage, most notably a conspicuous black hood contrasting with yellow cheeks and forehead. Females vary greatly in the extent of their black hood, and early reports were mistaken in identifying dark females as subadult males (Palmer 1894). Adaptive significance of such variation in female plumage remains unknown. Adults retain their plumage coloration year-round, and there is no noted geographic variation in appearance.