In compliance with the Endangered Species Act (ESA), the National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS) must designate critical habitat for each species under its jurisdiction listed under the ESA. Critical habitat is defined as “specific areas within the geographical area occupied by the species at the time of listing, if they contain physical or biological features essential to conservations, and those features may require special management considerations for protection” and “specific areas outside the geographical area occupied by the species if the agency determines that the area itself is essential for conservation.”
Over 100,000 km2 have been designated as critical habitat for spectacled eiders. The critical habitat includes the Yukon-Kuskokwim Delta, Norton Sound, Ledyard Bay, and the Bering Sea between St. Lawrence and St. Matthew islands. These areas are important breeding, molting, and wintering areas for the spectacled eider.