Using mist-netting and observational surveys in southeastern Arizona, we documented use of habitat by 12 species of birds that migrate to this Mexican monsoon region to molt. During the drier monsoon season in 2007, higher proportions of molt-migrants congregated at riparian areas. During the wetter monsoon season in 2008, a wider range of habitats was used. Molt-migrants generally selected habitats similar to those of their breeding territories; however, in some cases, species appeared to shift habitats for molt, in response to environmental effects. For example, high use of grasslands by molting Lucy's warblers (Oreothlypis luciae) in 2007 and by lazuli buntings (Passerina amoena) and lesser goldfinches (Carduelis psaltria) in 2008 suggests variable responses to relative strength of the monsoon season. Our results underscore the need to conserve native grasslands and riparian areas; habitats in which we detected molt-migrants most frequently. Our results also indicate the need to conserve a mosaic of habitats to account for adaptive selection in response to variable environmental conditions.