Although generally thought to be relatively rare in the fossil record, bird bones are more common then most paleontologists would admit. The usual explanation for the lack of fossil birds is blamed on their bone construction. In order to be light enough to fly, bird bones are hollow with thin walls in the shaft. Thin walls mean the bone can be easily broken and thus quickly destroyed before they have a chance to become fossils. A lack of fossil bird bones results in a lack of knowledge about the fossil history and evolution of birds. This general lack of detailed knowledge of fossil birds, however, is more likely a reflection of the relative scarcity of paleontologists that work on fossil birds rather than the material itself. Actually, bird bones show up frequently as fossils and are collected, only to be relegated to a museum drawer where they languish until one of those relatively rare paleontologists with the knowledge and background to know what bird a particular bone represents rediscovers it in the collection.
Fossil bird bones are certainly common at Hagerman where at least one good identifiable bird bone shows up every time we conduct paleontological surveys on the Monument. At the present 26 different species of fossil bird have been described from Hagerman. This makes Hagerman third in North America for the number of fossil birds known from late Pliocene Blancan localities. The other two sites, Macasphalt, Florida with 42 species and San Diego, California with 36 species owe the larger number of species to their location. Both represent coastal deposits and include large numbers of sea birds.
Included among the 26 species of fossil birds found at Hagerman are 10 species which were first described based on Hagerman specimens. Hagerman has the distinction of having two of the most eminent avian paleontologists, or if you prefer paleo-ornithologist, study and describe its fossil birds. The first was Alexander Wetmore, Secretary of Smithsonian and leading student of fossil birds during the first three-quarters of this century. Fortunately for Hagerman the fossil bird bones collected during the Smithsonian expeditions did not remain forgotten in a drawer and in 1933 Wetmore described the bird material collected from 1929 to 1931 . After the last Smithsonian expedition in 1934 there was a lapse until the 1950's when Claude Hibbard of the University of Michigan began work in the area. Hibbard did not work on birds but rather small animals like mice and voles. However, Hibbard did appreciate the importance of the bird bones he and his students found and made arrangements for another famous paleo-ornithologist, Pierce Brodkorb, of the University of Florida to study the fossils. In 1958, 25 years after Wetmore's publication, the second paper on Hagerman's fossil birds appeared. Among the species described by Brodkorb was a new species of swan, Olor hibbardi, named after Claude Hibbard in recognition of his efforts at Hagerman.
Like many of the fossils found throughout Hagerman Fossil Beds National Monument birds are often represented by single bones or the ends of bones. While it is true that the thin walls of the shaft of a bone are easily broken, the ends are often robust enough to remain intact and these are what we find on a regular basis. The part found by Hibbard and described by Brodkorb was the end of one of the bones of the lower leg, the tarsometatarsus, where the toe bones attach. While that may not sound like much to work with, it happens to have a very distinctive shape, since it has three points of attachment for those toe bones. Careful comparison of the fossil specimens to the same bone in modern swans and with other fossil swans showed that although there were similarities to the living Tundra Swan, the overall differences in size, proportions and general structure distinguished the bone from all known swans. Brodkorb felt it represented a distinct and new species. Since only the end of one bone was originally described there's not much we can say about Hibbard's swan except that we know it was present at Hagerman and its general size. At the moment Hibbard's swan may seem to be mute, but continued work at the monument will undoubtedly produce other bones that will fill out its skeleton and tell us more about this species. Perhaps one summer we will be able to trumpet a new discovery.
Did You Know?
The zebra-like horse fossil Equus simplicidens was originally named Plesippus shoshonensis by Dr. Gidley, Smithsonian paleontologist, who led the 1929 excavation at Hagerman. He felt the fossil was different enough to represent a new species distinct from any other fossil horses.