Activités diurnes du Canard chipeau pendant son hivernage en Camargue. Relations avec les variables environnementales et sociales

Abstract

Diurnal activity budgets of Gad wall Anas strepera L. wintering in the Camargue (Southern France) are analysed from October 1985 to March 1986 in relation to some environmental and social variables. Along the winter cycle, the 2 main activities are feeding and resting, they are inversely correlated (r = — 1,00, P < 0,01) : from October to March, there is an increase in resting time and a decrease in feeding time. Among the variables analysed, time (month effect) as related to physiological conditions of birds, and water level, seem responsible of the winter strategy of Gadwall. This strategy is characterized by the storing of fat until December, then by a reduction of energy expenses following the natural increase of water level, which makes their food resources unavailable. Consequently, the reserves stored at the beginning of the winter are crucial to allow the survival of the species throughout the winter. The fat reserves necessary for migration and reproduction are probably not built-up in the Camargue.