In Algeria, nesting mallard were observed by Boumezbeur (1990). The present work is a preliminary contribution to the knowledge of the reproduction of Mallard (Anas platyrhynchos ) at Lake Tonga (North- eastern Algeria ) , why regular trips were made during the breeding season 2011. From March until the end of April, several nests were identified in the study area where the first spawning was noticed on March 27th and the last on June 17th.Most nests are built on the banks of the lake to the inner holes of tree trunks of alder Tonga, above the water surface about 48.807 ± 18.754 cm, surrounded by dense vegetation. The morphological parameters of nests studied showed: mean outside diameter is 29.385 ± 4.519 cm, average internal diameter is 19.000 ± 1.985 cm, the height of the average nest is 10.923 ± 5.346 cm; Thus statistical analysis shows a positive and significant correlation between internal diameters and outer diameters nests. The measure Duks Mallard eggs is average length is 56.203 ± 2.446 mm , an average width is 38.976 ± 2.031 mm and an average weight is 52.648 ± 4.539 which positive and significant correlations were noted between the different measurements of eggs ( length, width and weight ) . The study of reproductive parameters showed a mean clutch size of 8,923 ± 3,451 eggs for female, an incubation period ranging from 26 to 28 days and a high hatching rate of 92.307 ± 27.735 %.