Lesser scaup duller and have hardly any white at the bill base. Both sexes have white secondary remiges, a blue-grey bill with a black "nail" at the tip and grey feet; the drakes have a bright yellow iris, while that of females is orange or amber and that of immatures is brown. Downy hatchlings look much like those of related species, with dark brown upperparts and pale buff underparts, chin, supercilium and back spots. These birds are not very vocal, at least compared to dabbling ducks. Hens give the namesake discordant "scaup, scaup" call; in courtship drakes produce weak whistles. Hens vocalize
What Bird is That? all-time best seller in Australian natural history and is still in print today. While sales and stature of Cayley’s original collection continued to grow, the prolific artist and ornothologist Cayley was working on a much more ambitious project – his so-called “big bird book”. From about 1918, he was creating illustrations of subspecies, plumage stages and eggs (now lost) of all known Australian birds. The project was incomplete at the time of his death in 1950, although the illustrations were all but finished. The ornithologist Terence Lindsey revived Cayley’s plans in the 1980s, creating the last and most significant revision