The breeding ecology of Mallard Anas platyrhynchos at Lake Tonga, north-eastern Algeria

Abstract

The breeding ecology of Mallard Anas platyrhynchos was investigated at Lake Tonga, north-eastern Algeria, which is at the southern edge of the species’ range in the Western Palearctic. Breeding was mainly carried out in stumps of alder carr (Alnus glutinosa) that border the northern limit of the lake. The breeding season was relatively short, spanning two months. Laying occurred mainly in April but continued until end of May. The average clutch size was 8.4 ± 1.9 eggs (N = 19 clutches) with 10 eggs being the modal clutch. The overall nesting success was 54% (N = 29 clutches), whereas predation accounted for most nest failure (76%). As often happens in arid climates and instable habitats, breeding outcome was significantly and negatively related to egg-laying date with precocious nests conferring better survival to eggs. In contrast, nest predation was positively associated with a deferred laying date. Seven cases of interspecific brood parasitism were recorded, all involving the Mallard and the Ferruginous Duck Aythya nyroca, with both species acting as either a host or a parasite. Nests in dense vegetation were more likely to harbour this interspecific interaction.