In flight, the wings are brown above and black below, with no white markings, and a white crescent on the rump contrasts with the black tail.[15][16] All plumages are fairly similar, but the female is slightly smaller and duller-plumaged than the male. The juvenile has paler underparts, and appears generally duller, especially on the flanks.[5] There is a complete wing moult after breeding, and birds then seek the cover of dense wetland vegetation while they are flightless. Body feathers may be moulted throughout the year, although each feather is replaced only once annually.[17]