The Trumpeter Swan, Cygnus buccinator, is the largest native North American bird, if measured in terms of weight and length, and is (on average) the largest living waterfowl species on earth. It is the North American counterpart of the European Whooper Swan.
Their breeding habitat is large shallow ponds and wide slow rivers in northwestern and central North America, with the largest numbers of breeding pairs found in Alaska.
The female lays 3-12 eggs on average in a mound of plant material on a small island, a beaver or muskrat lodge, or a floating platform. The same location may be used for several years. The eggs average 73 millimetres wide, 113.5 millimetres long, and weigh about 320 grams. The incubation period is 32 to 37 days. These birds often mate for life, and both parents will participate in raising the cygnets, but only the female will incubate the eggs. The young are able to swim within two days and usually are capable of feeding themselves after at most two weeks. The fledging stage is reached at 3 to 4 months.
Source:http://en.wikipedia.org/wiki/Trumpeter_Swan – 26.09.2011