The aim of our study was to elaborate a new biotechnical breeding system of mule ducks improving its sustainability. Four flocks of 2400 mule ducks were successively raised on classical grass free ranges (n=2) or with trees (n=2) between 4 and 12 weeks. Half of the ranges (one of each type) have been divided in two parts to allow rotation at 8 weeks. The instantaneous stocking density of ducks under rotation was twice (3 m 2 per duck instead of 6). The presence of trees can favour growth and live body weight at 12 weeks, being improved two fold over four. By contrast rotation can lead to lower growth performances, but these deleterious effects disappear after two weeks force feeding and thus, liver and breast muscle production are finally not affected. With rotation, ducks appear often more dirty and with less feathering. Presence of trees can enhance the dirtiness of ducks, but they improve the quality of feathering. During sunny days and hot temperatures ducks appreciate to stay in the shadow under the trees. However it does not improve their distribution in the range as far they keep close to the drinkers. Tree growth also seems to be influenced with their distribution in the range. When harvesting grass, the longer time without duck on half of the range in case of rotation can allow bringing off a larger amount of biomass. The soil analysis shows an increasing of organic matter due to leaves in presence of trees. The presence of trees seems comfortable for birds, it improve the visual aspect of the free ranges, and subsequently will produce valuable biomass.