Moulting mass dynamics of female Gadwall Anas strepera and male Wigeon A. penelope at Abberton Reservoir, southeast England

Abstract

Capsule Female Gadwall Anas strepera and male Wigeon A. penelope lost about 18% of body mass during flightless wing moult at Abberton Reservoir, southeast England – slightly greater than that recorded for other dabbling ducks but less than among Pochard Aythya ferina at the same site. Results, while consistent with the ‘moult stress’ hypothesis, also support the hypothesis that dabbling ducks deplete accumulated fat stores to enable exploitation of moulting habitats that are safe from predators, but which do not enable these ducks to balance their energy budgets during the flightless period.