At least once a year, birds face the energetically demanding task of molting all their flight and body feathers. As a result, most birds avoid an overlap between molt and other costly activities during the annual cycle (e.g., raising young, migrating). Most Nearctic–Neotropical migratory birds undergo an entire prebasic molt at the end of the breeding season, before fall migration, and some also go through a second, pre-alternate molt of body feathers on the wintering grounds to refurbish their breeding plumage before reproduction (Pyle 1997, Froehlich et al. 2005). Even so, some birds employ a strategy of molt-migration, delaying some or all of their prebasic molt until after fall migration begins (Stresemann and Stresemann 1966). This phenomenon is relatively common in shorebirds, and nearly half the Neotropical migrants molt at least some feathers south of the breeding grounds (Leu and Thompson 2002). However, molt-migration is not nearly as frequent in passerines (e.g., only 7 of 53 wood warblers are reported to complete at least some of their prebasic molt outside of the breeding grounds: Vermivora peregrina, V. celata, V. luciae, Dendroica petechia, D. pensylvanica, D. kirtlandii, and Protonotaria citrea; Pyle 1997), and it also appears to vary geographically, occurring more commonly in western North America (Rohwer et al. 2005).