There is no way to just look at a swan and determine if it is pregnant. We are still within the window of nesting season for the mute swans so the swan could still lay eggs. On another note, are you sure that you have a male and a female swan? Male swans will mate with male swans, build a nest and sit on the nest. Obviously, no eggs. Female swans will mate with female swans, build and sit on a nest and sometimes produce eggs, obviously not fertile. The Regal Swan