Aythya 1st-winter male comparison
Greater Scaup (left), Lesser Scaup (middle) and Ring-necked Duck. These ducks show average differences in molt timing well, with Ring-necked being earliest, scaup being latest with Greater averaging later. In addition to structural differences, note the heavier barring on Lesser Scaup. I have recently starting wondering if this is a fairly good trait for 1st-year birds that have replaced these feathers.