San Diego County, California, US
I think it may be a female Goldeneye. It was frequently diving in the pond.
Tingley Beach ponds at Albuquerque, Bernalillo Co., New Mexico, USA.
Goldeneye and Whistler are common names for a species of small tree-hole nesting northern hemisphere seaducks belonging to the genus Bucephala. The plumage is black and white. Goldeneyes eat fish, crustaceans and other marine life. The "Whistler" name comes from the noise their beating wings make in flight.