The presence of white primary shafts separates shovelers from all other North American ducks. All birds having specula that are more than half gray or dull non-iridescent green are females. All males and a few adult females have iridescent green on more than half of their secondaries.
Most females show cream edging on the lesser and middle coverts.
This often covers all these feathers, particularly on adult females. Immature males may show a few cream colored edges on feathers near the alula. The tertials of immature males are brownish and much frayed, while those of adults and first winter immatures are greenish black and much longer. The tertial coverts of the immature male are brownish black and often show a frayed fringe. Adult tertial coverts are blackish, often washed with blue.