In this study we present data about local distribution, abundance, and habitat preferences of Black-headed Duck (Heteronetta atricapilla) in central Chile. Black-headed Duck is an endemic species of southern South America and the only obligate brood parasite whose ducklings needs no further parental care after incubation of the eggs. From July 1993 to January 1998 we monitored populations in 19 wetlands of the Mediterranean distribution is restricted and its presence is strongly associated to habitat with emergent vegetation. These results suggest that, populations located on the occidental side of the Andean highland, would present ecological traits strongly associated with rarity and high vulnerability.