Minnesota Valley National Wildlife Refuge. Trumpeter Swans were once common and widespread. Over-harvested by the feather trade, by 1935 only 69 birds remained. Reintroduction and strict management saved Trumpeter Swans. In 2000, about 2300 birds were censused; by 2010 the population is thought to be over 46,000 (Wikipedia). Now there are over 2400 wild Trumpeter Swans in Minnesota alone (MN DNR). The DNR notes that the main threats to swans include ingestion of lead shot, habitat destruction, collisions with power-lines, and illegal shooting.
Adults are the largest of the North American waterfowl. They are usually all-white. Sometimes their heads and necks sport a golden-brown stain, obtained from the iron-rich water and mud in which they often forage (Mitchell and Eichholz 2010).