In March 2017, I watched a lone pair of beautiful Trumpeter Swans working the open water just above the Stoddard Dike. Today there were 4 pair!
The Trumpeter Swan is a huge bird, with a wingspread up to 10 feet! But notice the very black bill which makes an almost perfect triangle and stretches right to the eye.
Image below is of a Tundra Swan, which is just slightly smaller and has a more curved bill and a light spot near the eye. Tundra Swans pass through in the Spring migration to the North, but will be seen in large groups. The Trumpeter, which was first established in Iowa in the last decade (I believe) now nests on the Upper River. Still very unusual to see.
Tundra Swan Image for comparison.