疣鼻天鵝 Cygnus olor

Huge white bird with long neck, reddish-orange bill, and black face. Adults have a black knob on top of the bill. Immatures are dusky brown with a gray bill. Native to northern Europe and Asia, but introduced in many regions, where it is now common on ponds, lakes, and calm coastal waters. Very aggressive toward native waterfowl. Often seen in pairs or small family groups.