Trumpeter swans are the largest waterfowl in North America, and easily the biggest flyers in Yellowstone. The wingspan of males (cobs) can reach seven feet. Cobs weigh between 25 and 30 pounds, while females (pens) weigh 23 to 27 pounds. The trumpeter is generally bigger and heavier than the eagle.

The trumpeter swan, native only to North America, was once headed toward extinction south of Canada. By the mid-1800s, market hunters had almost exterminated the trumpeter. They were slaughtered in great numbers for their plumage, used to decorate ladies' hats. By the 1830s, fewer than 100 birds remained. Congress set aside a wildlife refuge west of Yellowstone to facilitate trumpeter recovery. In recent years, the Park Service has also taken measures to assist the trumpeter, including nesting islands to protect nests from coyote predation.

Where to find them
Look for Swans along the Madison and Firehole Rivers. There is almost always a nesting pair on the Madison and depending on the time of year watch for cygnets. The Yellowstone River just south of Canyon is another good spot to look for Swans.