Endemic to the island of Hispaniola, the Green-tailed Warbler (or Green-tailed Ground-Tanager) has presented considerable problems to systematists attempting to classify it, having been variously considered a warbler, a tanager, or even just ‘dumped’ in the taxonomic equivalent of ‘don’t know’, as Incertae Sedis. It is a slender, rather long-tailed and distinctively plumaged bird, predominantly green above, with whitish-gray underparts, a gray crown and nape, and red irides. Two subspecies are generally recognized; although their ranges demand re-evaluation and clarification, M. p. vasta is possibly restricted to the offshore Isla Beata. The Green-tailed Warbler usually occurs in pairs or as part of mixed-species flocks, at least in the non-breeding season, and from sea level to well over 2000 m, although it is typically commonest at middle and high elevations. The species is found in a variety of well-wooded habitats from desertic thorn scrub to moist broadleaf forest, and it is principally restricted to the Dominican Republic but also ranges narrowly into southeastern Haiti.