環頸潛鴨 Aythya collaris

A relatively small diving duck with a tall peaked crown. Males are handsome with glossy black head and back, clean gray sides, and a brighter white spur on the side. Females are grayish-brown, often with a paler patch at the base of the bill and a white eyering. Both sexes have a white band near the tip of gray bill. Also note gray, not white, wingstripe in flight. Usually favors small bodies of water, such as beaver ponds and cattail marshes, but also occurs on larger lakes, rivers, and bays. Can be found in mixed flocks with other diving ducks, although usually in smaller numbers than scaup. Compare with both species of scaup and Redhead (especially females).