_Plumages._--The Colima warbler differs from its nearest relative, the Virginia's warbler, in being larger; darker, less gray, above; crown paler; rump and upper tail coverts darker and richer in color; yellow of throat and breast absent or, if present, more green and more diffuse; sides and flanks more brownish; crissum darker, more aniline yellow; sexes much more nearly alike. The adult female Colima warbler is slightly darker than the male and is more brown below. It is apparently never yellow on the breast. The juvenal plumage (known from only one specimen) differs from the adult plumage in lacking the crown spot and in having two buffy wing bars. The rump is also much more yellow (less green) and the crissum is more yellow (less orange). The young Colima warbler differs from the young Virginia's warbler in having a larger bill, darker plumage, and a less ochraceous rump. The fall plumage differs from that of the spring in being "darker and browner throughout, the gray of head a good deal obscured by deep olive or light brownish olive; crown patch orange rufous; under parts darker with whitish area in middle of belly more distinct and under tail-coverts duller, more nearly aniline yellow" (Bangs, 1925). George Miksch Sutton's fine color plate (Van Tyne, 1936, frontispiece) of the Colima warbler is apparently the only published figure of the species. _Behavior._--In Texas, the Colima warbler was observed feeding on insects (which were not identified), but nothing further has been recorded about its food. All observers seem to agree that it is not a shy bird, although in its preferred cover, the female seems elusive and nests are difficult to find. Sutton has remarked that they are "rather deliberate, even vireo-like in their movements" (Van Tyne and Sutton, 1937). In the Chisos Mountains, they frequented especially the young maples and deciduous oaks along the banks of the dry, boulder-strewn stream bed, and elsewhere on the steep mountain slopes their preference for clumps of small oaks was noted.