This is chiefly a prairie breeder, south of most of the Greater Scaups, wintering south to the Gulf states.
It is mainly a bird of passage in Ontario, though a few may be found in summer and winter.
I have found it mainly in shallow, marshy habitat, not in deep water where the Greater Scaup is often found in great rafts.
From the Greater Scaup it is most readily distinguished by the short white wing stripe in flight
and on the water at close range by the purple gloss on the head and somewhat more puffy head shape.
Dr. J. Murray Speirs