The ring-necked duck (Aythya collaris) and the scaup (Aythya marila) are two species of diving ducks that are often confused with each other. Both species have similar plumage, but there are a few key differences that can help you to identify them.
The ring-necked duck is slightly smaller than the scaup, with a body length of 16-18 inches and a wingspan of 28-32 inches. The scaup is 17-20 inches long with a 32-36 inch wingspan. Both species have dark brown or black plumage, but the ring-necked duck has a distinctive white ring around its neck. The scaup has a white patch on its face, and its back is more black than brown.