The distribution of the Whiskered Tern (Chlidonias hybridus) is scattered, numbers fluctuate and they are threatened in many regions. Its breeding ecology has only occasionally been studied so far. It is relatively common in some North African wetlands. This study was carried out on Lake Tonga, northern Algeria, south of El-Kala (3651’N; 0820’E) in 1996 and 1997, with 169 and 215 initiated clutches studied, respectively. Basic characteristics of the Whiskered Tern breeding ecology studied were: laying date, clutch size, hatchling number, nest size and shape and egg size. Hatching success differed significantly between 1996 and 1997, probably due to weather. Laying date did not influence breeding parameters. Clutch size and hatching success were correlated with size and shape of nests. Hatchability was also correlated with egg length (negatively) and mass (positively). Relationships between breeding characteristic in relation to weather are discussed.