Body Mass and Pectoral Muscle Size Changes in African Waterfowl During Moult

Body mass and organ size dynamics during flight-feather moult vary among waterfowl species. To better understand adaptations of the African waterfowl, we measured how body masses of Spur-winged Goose (Plectropterus gambensis),South African Shelduck (Tadorna cana), Yellow-billed Duck (Anas undulata), Red-billed Teal (Anas erythrorhyncha) and Southern Pochard (Netta erythrophthalma) change during flight-feather moult. We further assessed how pectoral muscle size of Spur-winged Goose and South African Shelduck varied during the same period of flight-feather moult. Our results indicate that Spur-winged Goose and South African Shelduck underwent atrophy and subsequent regeneration of the pectoral muscles, while their body mass decreased at the onset of moult and later stabilized from the time when flight feathers were two-thirds grown until moult was completed. Body mass of Yellow-billed Duck and Red-billed Teal decreased from the onset of moult until the mid-point but thereafter increased rapidly, returning to pre-moult levels by the time moult was completed. Southern Pochard gradually lost mass from the start of moult almost until moult completion, at which time mass increased slightly.We conclude that African waterfowl exhibit different fluctuations in body mass and pectoral muscle size during flight-feather moult. Taken together, these findings suggest that no single hypothesis can fully explain the interspecific differences in the moult strategies of African waterfowl as reflected in changes in body and pectoral muscle conditions.