Nest site selection and breeding ecology of the Ferruginous Duck (Aythya nyroca) in Algeria

Abstract

Ecologically, the Nature Reserve of Tonga Lake (northeastern Algeria) is very important for waterbirds. This study investigates breeding biology of an emblematic species of this region: The Ferruginous Duck (Aythya nyroca), a duck ranked globally 'Near Threatened' on the IUCN Red List. This study aimed to determine wetland environmental variables influencing nest site selection and breeding success of the species. Over two successive breeding seasons (2016 and 2017), the effects of habitat characteristics and nest traits on breeding parameters of 50 nests constructed on alder carr of the lake and offshore floating vegetation islets in the center of the waterbody were analyzed using generalized linear models (GLM). Clutch size averaged 9.8 ± 0.7 eggs (range: 2–26 eggs) with 66% hatching success. Desertion of the nest (i.e. nest abandonment by the parents during the period of egg-laying and/or incubation) was the main cause for breeding failure (18% of total nests). Clutch size was positively related to nest surface and nest depth, but it decreased with the increase in the distance of nest on the vegetation platform to water. GLM revealed that breeding success was positively associated with late clutches; with a negative effect of conspecific nest density on clutch size and breeding success. Nest-site choice is resulted from interspecific competition and/or is affected by the reduced number of favorable nesting sites. Nine nests (18%) were parasitized by the same species of which 67% were central nests. Only 2% of the nests studied were parasitized by Oxyura leucocephala nesting at the site. Possible explanations of nest site selection of Aythya nyroca in the study area are discussed. Variations in selection pressures may explain the relationships between the choice and characteristics of nest site in the Ferruginous duck at Lake Tonga.