This shot of a female Greater, shows the wide black nail but on hen Greater this dark coloration bleeds out across the bill away from the nail, sometimes running all the way across the end; this is rarely seen on a Lesser Scaup. The white around the bill is wide and well defined and she exhibits the cheek patch that is often shown as a field mark in some older guides but occasionally Lesser hens will show a less obvious mark. Again this is a bulky bird.

There are many other differences such as the length of the white wing stripe (running out onto the base of the primaries on Greater but restricted to the secondaries on Lesser) and the differences in the vermiculation on the backs of the males, etc., but these photos meet the challenge Head On.