Idaho is one of the few localities in North America where differentiating between Trumpeter Swan and Tundra Swan is a necessity... at least if we want to be carefully accurate in our observations. All too often I've heard "It looked too big to be a Tundra" or "There was no yellow on the bill" or even "They kept away from the others, so...."
Idaho Migratory Waterfowl Stamp, 1990-1991 - Trumpeter Swan
Idaho Migratory Waterfowl Stamp, 1990-1991 - Trumpeter Swan
Unfortunately all of the preceding are not good reasons in and of themselves to make an accurate determination. And although Trumpeter Swans are regularly seen in western Idaho, I wonder a bit about numbers often reported, especially considering the obvious drop-off in occurrence when moving away from the eastern Idaho breeding areas. Even the map utilized at the conclusion of this piece designates a "non-breeding, resident population" in western Idaho.... Don't mistake that as meaning the birds are there all year long. It means nothing more than they can be present during non-breeding times (non-summer or breeding season)....
David Sibley makes some good (and as usual, well illustrated) points, primarily based on a visit to Skagit Valley of Washington State to view both species. The material is worth careful consideration, especially at this time of the year:
David Sibley makes some good (and as usual, well illustrated) points, primarily based on a visit to Skagit Valley of Washington State to view both species. The material is worth careful consideration, especially at this time of the year:
Personally, I have found two id points to be most helpful in sorting out these two very similar species. First, I have not found the head shape to be a variable between the two. As with white-cheeked geese, taking careful note of the relationship between bill and head is very telling. With practice, it is quite easy to see the much more rounded shape of the Tundra Swan head, which is even more accentuated by the steeper slope of the bill in relation to the head. Trumpeter Swan head/bill relationship is much more continuous in nature, from bill tip to top of head, which often seems quite peaked with what can even be an abrupt point at the rear of the crown. A head-on view of a bird might be more of a challenge, but usually the bill/head relationship identification point is diagnostic of itself. Another little referenced but extremely useful point when looking at a bird "head-on" is the fact that the bill outline of Trumpeter Swans forms a "V," whereas that of a Tundra is much more of a "U."
A second point that can be very helpful is the positioning of the eye. Even when viewing the suggested 10% of Tundra Swans which have no yellow on the bill at all, the eye still seems to be "disconnected" from the bill, whereas in Trumpeter Swans the eye and bill blend together into an indistinguishable whole. I find that even at a distance this trait is useful and, with practice, can be easily noted.
Here are some often used identification points that should not be relied upon, especially if used in isolation:
1. apparent body size of the individual bird
2. presence of (or lack of) yellow on the bill
3. body shape and structure
4. association with or away from other swans
5. leg color
6. isolated vocalizing birds - "bugling" of Tundras can sound strangely like the "trumpeting" of Trumpeters. "Whistling" (hence the former name, Whistling Swan) is not the only vocalization of a Tundra Swan.
Also, of interest are the total reported Trumpeter Swans in the Great Backyard Bird Count, beginning in 1998 through 2008, for Idaho, Oregon, and Washington:
Washington: http://gbbc.birdsource.org/gbbcApps/report?cmd=showReport&reportName=SpeciesCity&species=truswa&state=US-WA&year=2008
One issue also worth mentioning is the identifcation of first year birds. Bill size and shape is not reliable on young birds, particularly since young Tundra's bills seem quite "large." Young birds (gray-brown in both species) which have pure white on scapulars in December and January are always Tundras (Trumpeters are still in full juvenile plumage during this time period). During the months before December, when juveniles can seem quite similar in plumage, Trumpeters are said by many to have a more patterned, scaly look resulting from lighter feather edges. I cannot personally speak to this potential differentiation.
Of instructional value may be detailed range maps for both species (provided by southdakotabirds.com):
Tundra Swan
Trumpeter Swan
(As always, your critical comments about the helpfulness, accuracy, and reliance of any identification material is welcome.)
One issue also worth mentioning is the identifcation of first year birds. Bill size and shape is not reliable on young birds, particularly since young Tundra's bills seem quite "large." Young birds (gray-brown in both species) which have pure white on scapulars in December and January are always Tundras (Trumpeters are still in full juvenile plumage during this time period). During the months before December, when juveniles can seem quite similar in plumage, Trumpeters are said by many to have a more patterned, scaly look resulting from lighter feather edges. I cannot personally speak to this potential differentiation.
Of instructional value may be detailed range maps for both species (provided by southdakotabirds.com):
Tundra Swan
Trumpeter Swan
(As always, your critical comments about the helpfulness, accuracy, and reliance of any identification material is welcome.)
1 comment:
Again, excellent comments. In my quest to see a Trumpeter Swan we went to the Drylake Area south of Nampa. We saw a few swans that had all of the characteristics you said not to use to distinguish the swans. After about a half hour study we were able to plainly see the differences between Tundra and Trumpeters in the shape of where the beak attaches to its head.
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