Scarecrow 180 Bird Dispersal System is a stand alone unit that emits 10 different distress calls of birds to make other problem birds think there is danger and so they stay away from the area. Covers up to 20,000 square metres this bird repelling unit is ideal for use in public parks, shopping centres, public arenas, airports, marinas, on yachts and ships or other large areas where bird pest control is needed.