Le canard Souchet (Anas clypeata L.) hivernant en Camargue : alimentation, comportement et dispersion nocturne

• Main Authors: PIROT, Jean-Yves, PONT, Didier
• Other Authors: Bureau international de recherche sur les oiseaux d'eau (BIROE), Slimbridge Glos. GL2 7BX, GBR, Université de Provence Saint Charles, Laboratoire d' Hydrobiologie et d'Écologie, place Victor-Hugo, F-13331 Marseille Cedex, FRA
• Format: Article in Journal/Newspaper
• Language: French
• Published: Société nationale de protection de la nature et d'acclimatation de France, Paris (FRA) 1987
• Subjects: Aves; Régime alimentaire; Comportement alimentaire; Habitat; Ressource alimentaire; Rythme circadien; Nuit; Hiver; Camargue; France; Anas clypeata; Diet; Feeding behavior; Food supply; Circadian rhythm; Night; Winter; Shoveler
• Online Access: http://hdl.handle.net/2042/55253

Food habits, behaviour and nocturnal feeding areas of Shoveler wintering in the Camargue (Rhône delta, France) are documented from mid-summer to late winter. The diet is mainly composed of animal prey (81 % by weight), especially zooplankton. Food items are taken providing prey size is greater than 1 mm. The quality of ingested prey varies according to availability following artificial marsh flooding, rainfall, changes in water levels and the occurence of submerged vegetation. Cladocera (Daphnia magna) and insects (Sigara sp.) are predominant food items in late summer, Ostracoda and molluscs (Physa acuta) are ingested in autumn, while Copepoda (Calanipeda aquaedulcis) are the main food consumed during winter. From August to November, large amounts of food are consumed (circa 76.5 g dw/day : 10.1 % of the total body weight) and this allows the birds to lay down 65-68 g of fat reserves. Reduced diversity and amounts of prey from December onwards limit further improvement in body weight which remains stable throughout the winter. Time-budgets show that 53 % of the 24 hours is spent feeding, mainly at night, while swimming, resting and preening are largely diurnal activities. Despite a decrease in swimming and flying activities, the time spent feeding in late February (12.40 hours) is similar as that recorded in late autumn (13.00 hours). No spring hyperphagia is apparent fat stores needed for migration and reproduction must be acquired later in the season (and/or elsewhere) by feeding on higher prey densities at higher temperatures. Nocturnal space use shows that energy requirements are only met in two types of habitats. Freshwater marshes, managed for hunting, allow weight gain early in the season and shelter most of the spring migrants Shoveler also uses temporary marshes naturally flooded from October to February where prey densities are high enough to enable overwintering individuals to maintain fat reserves. The early flooding scheme in the Camargue is believed to be responsible for the dramatic increase in the numbers of wintering and staging Shoveler there in the last 15 years. In the fish-free temporary marshes, feeding Shoveler at an average density of 3.3 birds/ha remove approximately 14 % of the plankton available in one month. As a consequence, predation by Shoveler can be considered as an important parameter in the population dynamics of plankton communities