識別
Huge white bird with long neck and all-black bill. Immatures dusky gray-brown with pink on bill. Forages in shallow, vegetated wetlands reaching under the water for plants, and walks through corn stubble. Breeds in freshwater marshes and ponds. Winters on any open body of water where food is available. Extremely similar to Tundra Swan, but never shows yellow on bill. Also, note subtle features of face: facial skin is relatively broad where it meets eye, so the eye doesn't stand out, and border between white face and black bill is straight (curved on Tundra). From head-on, the border of the bill and forehead is usually pointed (straight or curved on Tundra). Often in pairs or family groups. Almost went extinct in early 20th century, but population has rebounded and been reintroduced to some areas.