Lesser Scaup (female) Aythya affinis Andrew Haydon Park, Ottawa, Ontario 16 November 2008 Lesser scaup very closely resemble their cousin the greater scaup (A. marila).  From a distance, it is virtually impossible to distinguish the two unless they are right next to each other.  However, when viewed up close, the shape and size of the head and thickness of the beak can be helpful field markers in identification.

Lesser Scaup (female) Aythya affinis Andrew Haydon Park, Ottawa, Ontario 16 November 2008 Members of the Aythya genus are divers, and normally are found in deeper waters, further offshore than the more typical dabbling ducks.  Large rafts of these species can be found on the Ottawa River, especially in Lake Deschênes, where the river widens to become a slow-moving lake.  More often than not, I have only ever seen these species from a distance, with the aid of binoculars or if I'm lucky enough to find a fellow birder with a sighting scope. However, on this particular overcast day, I found a female lesser scaup taking a nap onshore with a flock of mallards.  If it wasn't for her telltale white patch at the base of the beak, I probably would have mistook her for another sleeping mallard and moved on.

Cackling Goose "Richardson's" subspecies Branta hutchinsii hutchinsii Andrew Haydon Park, Ottawa, Ontario 2 November 2008