Birds living in desert environments have been the preferred models for the study of physiological adaptations to water scarcity. Passerine birds living in marine coastal habitats face similar problems, yet physiological adaptations to water conservation in such species have been poorly documented. We measured total evaporative water loss (TEWL) and rates of oxygen consumption (VO2) in three species of passerine birds dwelling in marine and fresh water habitats. Mass specific total evaporative water loss was significantly lower in the marine species, Cinclodes nigrofumosus, than in species inhabiting areas near freshwater sources. We found a positive relationship between TEWL and VO2. The ratio of TEWL to VO2 (relative evaporative water loss, RTEWL) showed significant variation among Cinclodes species, and was highest for the fresh-water living species, C. oustaleti and C. fuscus. The variation in TEWL found in Cinclodes is likely a consequence of differential exploitation of marine prey with high osmotic loads, which, in turn, may impose the need for water conservation