Despite its name, the Palm Warbler is among the northernmost of any Setophaga species. Described by J. P. Gmelin from a wintering specimen on Hispaniola, this warbler winters primarily in southeastern and Gulf Coast regions of the United States. Its breeding distribution generally corresponds to the distribution of bogs and fens in boreal forests of Canada and the northern United States. Among congeners, only the Blackpoll Warbler (S. striata) has a more northerly breeding distribution.
In addition to differing in its distribution, the Palm Warbler differs from other Setophaga species in being the most terrestrial member of its genus, feeding primarily on the ground or in short shrubs and trees, and in being essentially sexually monomorphic. It usually nests on the surface of bogs, beneath a short conifer. Because its nesting habitat is often remote and difficult to traverse, and its nests difficult to find, much remains to be learned about this species' breeding biology. Only one study (involving only ten nests) has focused on this warbler over the course of a breeding season ( Welsh 1971 ). But because this species is a common, conspicuous wintering bird, and is easily found on migration, much more is known about its life history during those periods.
Two subspecies of the Palm Warbler exist, easily identified in the field. The two forms inhabit separate breeding grounds but overlap on their wintering grounds. The Western Palm Warbler (S. p. palmarum) nests roughly west of Ottawa, Ontario, and winters along the southeastern coast of the United States and in the West Indies. The Yellow Palm Warbler (S. p. hypochrysea) nests east of Ottawa and winters primarily along the Gulf Coast. Studies on interactions of the two subspecies are needed.