In 1975, 3 types of waterfowl deterrent (a model falcon, a moving series of reflectors suspended from a frame, and a human effigy) mounted on floats, were tested for efficacy in deterring waterfowl from entering a series of small natural ponds in the boreal forest of Alberta. Only the effigy appeared to be effective; diving ducks of the genus Aythya were affected most. In 1976, the human effigy was tested on an artificial tailings pond that received aqueous and bituminous effluent from an oil sands extraction plant near Fort McMurray, Alberta. Twenty-seven effigies were deployed over the 150-ha pond. Their effectiveness was judged by comparing the number of waterfowl dying in and associated with this pond in 1975 (without deterrents) with number dying in and associated with it in 1976 (with deterrents). Kill figures in 1976 were significantly lower than expected on the basis of relative abundance of birds in the 2 years. We concluded that this decline was due to the presence of the effigies.