Habitat use by wintering Mallards (Anas platyrhychos) on the Gulf Coast Chenier Plain (GCCP) has received little study and quantitative data is needed for management of GCCP waterfowl. Radio-telemetry techniques were used to record habitats used by 135 female Mallards during winters 2004-2005 and 2005-2006 in south-western Louisiana. Habitat use was quantitatively estimated for areas open and closed to hunting, by general habitat types (i.e., marsh, rice, idle, pasture, or other), and for specific marsh types (i.e., freshwater, intermediate, brackish, or salt). Variation in these estimates was subsequently examined in relation to individual female, female age (adult or immature), winter (2004-2005 or 2005-2006), and hunt periods within winter (second hunting season [SHUNT] or post hunting season [POST]). Diurnal use of areas closed to hunting was greater during hunted time periods in winter 2005-2006 than in winter 2004-2005. Nocturnal use of areas closed to hunting was 3.1 times greater during SHUNT than during POST, and immatures used areas closed to hunting more than adults. Diurnal use of marsh was 3.3 times greater than that of any other habitat during both winters. Nocturnal use of marsh, rice, idle, and pasture were similar during both winters. Females used freshwater marsh habitats extensively (64.699.8% proportional use), whereas brackish and salt marsh combined was used less frequently (035.8% proportional use). These results suggest that freshwater marsh is important to Mallards and a high priority for restoration and management efforts.