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

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.Keywords: Anatidae, brood parasitism, clutch size, North Africa, reproduction, waterbirds, wetland

Nesting ecology of Ferruginous Duck Aythya nyroca in north-eastern Algeria

The status of waterbirds breeding in protected areas in North Africa needs constant monitoring because of a naturally fluctuating environment and permissive attitudes towards illegal activities likely to negatively affect population dynamics of threatened species. We present the results of a study conducted at a protected site, Lake Tonga, north-eastern Algeria, on a breeding population of Ferruginous Duck Aythya nyroca, a Near-Threatened duck subjected to considerable pressure from egg-pilfering and illegal hunting. Two distinct habitats within the lake were used by Ferruginous Duck: an Alder carr (Alnus glutinosa) and floating islets across the lake. The mean clutch size was 9.51 ± 1.84 eggs (N = 51 clutches) with hatching rate of 80.7% for successful clutches. Breeding success was low (37%) with predation (33%) and clutch desertion (17%) accounting for the majority of failed nests. The probabilities of nest failure and nest desertion increased with a delayed onset of egg laying. Predation was not significantly associated with egg laying date and vegetation cover, but late breeders nesting in dense vegetation seemed to suffer less predation. Conspecific brood parasitism was positively associated with nest size, whereas interspecific brood parasitism was marginally associated with water depth. We discuss different hypotheses concerning nest desertion, and argue that illegal hunting and disturbance may best explain why birds desert their nests.Keyword: Anatidae, anthropogenic pressure, breeding success, North Afric