The ecological niche describes a way of living that provides a species with adequate nutrition, an optimum environment and as few enemies as possible. For instance, several different species of water birds [ like ducks, pochard, goosander etc. ] can live together peacefully on the sea because each species prefers a different food or hunts for its food at different depths of water [ say, tufted duck prey at 4m, while goosander at 6m depth ] . The birds do not prey on each other's food, thus are not natural enemies.