Ring-necked Duck
Aythya collaris
Ring-necked ducks are small to medium-sized diving ducks with the following length, weight, and wingspan measurements: Length: 15.3–18.1 in (39–46 cm) Weight: 17.3–32.1 oz (490–910 g) Wingspan: 24.4–24.8 in (62–63 cm) The adult male is similar in color pattern to the Eurasian tufted duck, its relative. Males are a little bit bigger than the female. It has two white rings surrounding its gray bill, a shiny black angular head, black back, white line on the wings, a white breast and yellow eyes.
ID text from Wikipedia, CC BY-SA 4.0

Tufted Duck
Aythya fuligula
The adult male is all black except for white flanks and a blue-grey bill with golden yellow eyes, along with a thin crest on the back of the head. It has a prominent tuft on its head, which gives the species its name. The adult female is brown with lighter flanks, and is more easily confused with other diving ducks. In particular, some have white around the base of the bill, resembling the scaup species, although the white is never as extensive as that of those ducks. The female's call is a harsh, growling "karr", usually given in flight.
ID text from Wikipedia, CC BY-SA 4.0

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