Palaeornithology of the Mute Swan
The mute swan is of the order Anseriformes and the family Anatidae. The species name is Cygnus olor. This bird is native to Europe and Asia and also lives in the U.S. It was imported to America in the past and descendents of the imported ones now live in the wild. However, there is a consensus among some people that some mute swans were in the wild in America long before Europeans arrived on the continent.
Kathryn Burton presents her ideas in an article titled The Origin of the Mute Swan and how they came to be in America. In the section called Paleontological Considerations, she gives paleontological evidence pertaining to the theory. Burton says:
Fossils discovered at several sites in the United States represent a now-extinct mute swan genotype, described by Cope as "Represented by numerous bones, especially by four metatarsals, two of which are nearly perfect, indicating a species very near those now existing, but apparently distinct." (The Mute Swan was called Sthenellides olor at the time and it is named in these papers as Sthenellides olor, later changed to Cygnus olor, the species name used today.) Trumpeter swans were also found on the site, Fossil Lake, Oregon, dated as late Pleistocene in the definitive studies by Howard, making them more relevant to today than the earlier designation of Pliocene.
Analogous Pleistocene fossil material was discovered at Hagerman Fossil Beds National Monument. Pierce Brodkorb of the University of Florida described the specimen, later dubbed as Olor hibbardi. It is a Mute Swan homologue (G. McDonald, 2001). This study was canceled.
Convincing paleontological evidence suggests beyond reasonable doubt that mute swans, or swans homologous with mutes, occurred in North America in prehistoric times (Cirianca et. al. 1997). North American Miocene and Pleistocene swan fossil bones, consistently larger than in trumpeter or tundra swan material, have been identified as mute swans or swans homologous to mutes, and not trumpeters or tundra swans (op. cit.).
The skeletal architecture of mute swans is so distinctive that positive identification using modern investigative techniques is readily achievable (Savage pers.com). Trachea and syrnx size and shape are particularly instructive in that regard/Boyd, 1972).
More than 1000 Pleistocene bones of the Anatidae, discovered in the late 1880's at Fossil Lake, Oregon. Among the Fossil Lake material are bones of a fossil Cygnus species belonging to a homologous group of which the mute swan is a member (Wetmore 1959). The specimens represent a type of mute-like swan in which the trachea is not looped, distinctively unlike the looped trachea of both the trumpeter and tundra swans (Howard 1945). Initially named Cygnus paloregonus, this now-extinct species has skeletal features unlike those of the trumpeter, and is too large to be a tundra swan (Wetmore 1959).
Arizona has yielded a late-Pleistocene fossil of similar mute swan type (Howard 1956, Bickert pers.com).
Burton states the possibility that mute swans may have long ago migrated to North American from Siberia. She points out that the Kamchatka peninsula has a population of mute swans. That peninsula is in very close proximity to Alaska. Burton mentions other possibilities in this excerpt:
The parental stock might have originated in the New World or Old World, then pioneered to become established across the Northern Hemisphere. Eventually, the North American genotype became extinct, whereas the European morph survived into modern times, taking the Pacific Coast or cross Great Lakes Region.
Kathryn Burton is a well known wildlife conservation activist. She has been doing work pertaining to the preservation of swans.
Neal Robbins
P.S. The taxonomy of the mute swan is:
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Cygnus
Species: Cygnus olor
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