The Trumpeter Swan Society website holds many useful clues to help you distinguish North American Swans in the field. Spring migration brings new challenges so it’s a good time to test your skills. At www.trumpeterswansociety.org you can find a comparative chart with measurements of each species, sound recordings of their voices, a printable identification brochure, hints on behaviors and postures that clinch identification and other helpful tips. There is a whole page devoted to ‘head and bills’ with a cautionary note to use tips when birds are standing as this clue is far more difficult to discern in flight.
http://www.trumpeterswansociety.org/id.htm takes you direct to our Identification pages.
I (Peg) like to think of bird identification as a pleasant way to use those geometry skills learned long ago. You may not always have another species to use as a ruler against the swan you are looking at. If you do, it’s easy – just how much larger than the Mallard or Snow Goose is this bird? Your birding field guides lists sizes – make a handy reference chart for comparable waterfowl in your area. If you find a swan or swans on their own, try using geometry within the bird. The Mute Swan’s bill is distinctive while the other two species are not at first glance. However, if you focus on the length of the bill and hold mental measurement up against the birds head, a Tundra Swan’s bill from eye to tip will barely cover its cheek back to the neck. A Trumpeter’s bill if used in this way would extend way beyond the neck. Always remember that the shape of the head profile may vary between individual birds. Tundra swans, especially, have a wide range of head-bill shapes, some having very obvious concave bills, while others appear straighter. Color can give additional clues. Look carefully at the eye area for any yellow on the lore and to see if the eye is distinct from the bill as in the tundra swan. You will need a scope or a very close encounter to accurately discern color in most bills, but it may stand out in enlarged digital images.
As Trumpeters expand their range, it is critical that hunters recognize them quickly from far smaller Snow Geese. As we develop our Citizen Science Monitoring Project it will be imperative that observers know the difference. Take a moment to study our tips, head for the field where you may find a mix of species and please tell us what information you find most helpful and in general, how would you rate your confidence as you sort through the flock? Thanks to Loren Webster for sharing this photo from his photography blog.