The nest is built of a mound of vegetation in shallow water, on an island or at the edge of a lake.
Mute Swans are strongly territorial. During the breeding season they will aggressively defend the nest and their young, known as cygnets.
Mute Swans were introduced into North America in the late 19th century. A study of populations in the lower Great Lakes between 1971 and 2000 showed their numbers were increasing at a rate of 10% a years. This meant their numbers were doubling every seven years.