Using museum specimens, we documented the molt cycles and molting grounds of adult Lucy's (Vermivora luciae) and Virginia's (V. virginiae) warblers. During prebasic molts, both species replace all body plumage. Prebasic primary molt takes a mean of 71 days for Lucy's Warblers, but a mean of just 42 days for Virginia's Warblers. Prebasic molt occurs exclusively on the breeding grounds. We found no evidence of a prealternate molt in Lucy's Warblers, and limited evidence of a prealternate molt in Virginia's Warblers. In both species, the seasonal change in crown color is a function of the freshly replaced gray-tipped feathers acquired during the prebasic molt being abraded during the winter, such that the basal red coloration of those same feathers is exposed during spring. These species differ from other western-breeding passerines in that they do not appear to directly exploit the late season food resources in the southwestern United States and northwestern Mexico. This difference is suggested by the lack of a shift from northern parts of their breeding range to molt in those potentially more productive regions of the southwestern monsoon region. The possibility of winter territoriality may play a role in the rapid prebasic molt exhibited by Virginia's Warblers. On the other hand, the lengthy prebasic molt of Lucy's Warblers may be explained by the use of poor nutritional resources during late summer, and/or the lack of territoriality during late summer and winter. We conclude that our data, in conjunction with data from previous studies, suggest multiple contrasting molt migration strategies among breeding passerines in western North America.