All illustrations by Mike Langman
Goldeneye (Bucephala clangula) (above)
40–48cm. Eclipse male is similar to female, developing a brown head, but retains traces of white at base of bill.
Mallard (Anas platyrhynchos)
50–60cm. Moulting male resembles female, but has an all-yellow bill and a much more rufous chest.
Gadwall (Anas strepera)
46–56cm. Eclipse male looks like a small, greyish female mallard, but has a white speculum (wing flash).
Garganey (Anas querquedula)
37–41cm. A scarce summer visitor to UK. Eclipse male has a pale throat, dark cheek stripe and all-grey bill.
Teal (Anas crecca)
34–38cm. Easy to identify by its tiny size and green speculum (wing flash). Eclipse male near-identical to female.
Wigeon (Anas penelope)
42–50cm. A white forewing patch and bold chestnut tones separate the moulting male from the female.
Shoveler (Anas clypeata)
44–52cm. Unique bill confirms this species’ identity in all plumages; in eclipse, male is browner and plainer.
Tufted duck (Aythya fuligula)
40–47cm. In eclipse, male has just a hint of a crest, with dusky flanks and a brown tinge to black areas.
Pochard (Aythya ferina)
42–49cm. Male becomes drabber during eclipse, with a dull, mottled-grey (not glossy black) breast.
Red-breasted merganser (Mergus serrator)
52–58cm. One of two similar ‘sawbill’ ducks in UK; eclipse male looks like female, but with a white wing patch.
Goosander (Mergus merganser)
58–68cm. Larger than merganser, its close relative. White on wing helps separate moulting male from female.
Eider (Somateria mollissima)
60–70cm. Our largest sea duck. In eclipse, male is dark and mottled, with extensive white on wings.