I am a student at Iowa Stat University and we have a lake on campus that has been the home of a pair of two female mute swans for almost 9 years. It is a little known fact that both are female, becuase their names are Sir Lancelot and Elaine and as a tradition they are suppose to be a couple. The reason for the same sex is to discourage mating because the univeristy does not want to increase the population of the swans or have to worry about the young swans safety. However, although the swans do not mate or create fertile eggs, both females will still create a nest each year, lay eggs, and sit on that nest. My question is, do they get sad or depressed because the eggs never hatch? Or do they understand they aren't viable but just do the nest and sitting ritual out of habit?