We are not sure. It could be any of the above or none at all. Mute swans normally do not have trumpet like sounds but more muted. Do you have any Trumpeter Swans near you? Since we believe you are from the U.K., we know that the primary swans in your area are Mutes.

Sometimes the swans will make sounds as warnings or just as a means of communication. Are there any predators in the area or hunting? We wish we could be of more assistance, but there are just too many scenarios to render an educated guess. The Regal Swan