Bitter Lake National Wildlife Refuge is a protected wetland complex in central Chaves County, New Mexico, along the Pecos River where the Chihuahuan Desert meets the Southern Plains. Established in 1937 as habitat for migratory birds, it has become one of the most biologically significant wetland areas in the Pecos River basin. Oxbow lakes, sinkholes formed by dissolved gypsum, springs, and managed wetlands create unusually varied aquatic habitats that support at least 350 bird species, including large gatherings of sandhill cranes and wintering waterfowl. The refuge also shelters rare native fish and exceptional dragonfly and damselfly diversity. Its lakes and wetlands were designated a National Natural Landmark in 1980.