For our first pitfall I will begin with Anatidae, the family of waterfowl including swans, geese and ducks. The classic challenge in swan identification in North America is distinguishing between Tundra Swan (Cygnus columbianus columbianus, a.k.a. Whistling Swan, the North American version of Tundra Swan) and Trumpeter Swan (Cygnus buccinator), especially away from their breeding areas where they generally do not overlap.
During migration and winter, the two species do overlap, and they are typically shy. In many parts of the country, one or both species are considered rare, so they are typically observed in these areas by inexperienced birders, i.e. inexperienced with swan identification. To further complicate this identification challenge, these two species are thought to hybridize. While hybridization has not been observed in the wild, the widespread occurrence of swans intermediate in appearance lead to this conclusion.
Trumpeter and Tundra swans generally differ in size, vocalizations, molt timing and bill morphology. The bill is the most reliable difference because it is easily photographed, unlike the other three traits.
There are actually several traits of the bill itself that differentiate the two species. One of these is the color of the bill in the loral area, where it meets the eye. Tundra has a small yellow patch on the bill adjacent to the loral feathers that is missing from Trumpeter Swan’s all-black bill. Herein lies the pitfall. The yellow patch is variable in size and always hard to detect at a great distance. A significant percentage of tundra swans lack the yellow entirely, resulting in erroneous identifications of Tundra Swan as Trumpeter Swan.
To avoid this pitfall, remember that detection of a small yellow patch is diagnostic for Tundra Swan, but lack of yellow is NOT diagnostic for Trumpeter Swan. Furthermore, too much yellow could indicate one of the Eurasian swan taxa, Bewick’s Swan (Cygnus columbianus bewickii) or Whooper Swan (Cygnus cygnus). It is best to confirm the identification with additional traits. Can you identify these swans by their bills? See discussion of identifying traits with each of the photos below. [Click on a photo to see the commentary below the photo.]
Publication Date: 3 Nov 2025
References:
allaboutbirds.org/guide/Tundra_Swan/id.
Limpert RJ, Earnst SL, Carboneras C, Kirwan GM. Tundra Swan (Cygnus columbianus), version 1.0, in Birds of the World (SM Billerman, Editor), Cornell Lab of Ornithology, Ithaca, NY, USA https://doi.org/10.2173/bow.tunswa.01.
