For bird watchers, the Hagerman Valley provides a great variety of species to observe. While the diversity of fossil birds found in the Fossil Beds is not as great as the modern fauna, what we do know about the types of birds living in the Hagerman area more than 3 million years ago indicates that the diversity must have been just as good. As with the mammals, the fossil birds from Hagerman include forms that have no close relatives living in the area today. However, species probably would appear quite similar to their living relatives and an avid bird watcher would probably have little problem recognizing them. Many of the birds that lived in the ancient Hagerman ecosystem are types often associated with water. Many of their close living relatives can be seen on the Snake River or in the ponds and lakes of the area today.
During the summer one of the birds often seen either perched on tree limbs next to the river or flying overhead is the double-crested cormorant, Phalacrocorax auritus. Cormorants belong to the same group of aquatic birds as pelicans, anhingas, frigate birds, boobies and gannets. We tend to associate members of this group with the ocean and not inland Idaho. This is true for many members of the group. While many species of cormorants are found only near the ocean, a few, such as the double-crested cormorant are associated with fresh water and can be seen along the Snake River far inland from the ocean.
During the four summers the Smithsonian Institution worked at Hagerman, a few bird bones were collected. These were given to Alexander Wetmore, the leading student of fossil birds at that time and also on the staff of the Smithsonian. Wetmore published a short paper on these bird remains in 1933 and established for the first time the presence of birds as part of the Hagerman fossil fauna. The initial sample was small and mostly consisted of partial bones, but included in the sample was a bone of a cormorant. Wetmore considered it to be the same as the species living in the area today, Phalacrocorax auritus. Not much more was done on birds from Hagerman until the 1950's. Renewed interest in the Hagerman area and field work done by Claude Hibbard and his students from the University of Michigan produced a large sample of birds from the Fossil Beds. Some of the first material found was given to Pierce Brodkorb of the University of Florida to study. Included in the sample was more cormorant material which Brodkorb decided was a new species he named Phalacrocorax macer. One of the characteristics of Brodkorb's new species was that it was smaller than the species living in the area today. As Hibbard and his crews continued their work at Hagerman, more and more bird bones were found. Finally enough specimens were recovered that it seemed worthwhile to restudy the cormorants from Hagerman. This study was published in 1970 by Bertram Murray and resulted in the recognition that there was not one but two species of fossil cormorant at Hagerman.
Murray did not describe a new species of cormorant, but determined that in addition to Brodkorb's small species, there was a large species similar in size to the local living species called Phalacrocorax idahensis. This large species had first been described in 1870 by O.C. Marsh of Yale University, one of the leading paleontologists of the 19th century. As might be guessed from the name, Marsh's specimen was found in Idaho, but came from Castle Creek in Owyhee County. It was collected during the geological survey of Idaho conducted by Clarence King.
While most of the bones Murray had to study consisted of isolated specimens, he also had the advantage of a partial skeleton. While lots of individual bird bones have been found at Hagerman over the years, only one skeleton has been found. This was collected in 1966 by the Natural History Museum of Los Angeles County during their excavations at the Smithsonian Horse Quarry. Such a find is particularly valuable since it permits paleontologists to show conclusively that various isolated bones actually do come from the same species and not different animals.
Since the partial skeleton from the Smithsonian Horse Quarry included the same bone used by Marsh to create his fossil cormorant species, Phalacrocorax idahensis, Murray could be sure he had the same animal and not Phalacrocorax macer as identified by Brodkorb. The distinctive bone that permitted the recognition that two distinct species were present at Hagerman, has the rather strange name of carpometacarpus. Since birds are highly specialized for flying, many of their bones have distinctive shapes.
The carpometacarpus is actually the fusion of many bones including the wrist or carpus, and the bones that are the same as those in the palm of the hand or metacarpus, hence the name carpometacarpus. This bone plays an important role in how the bird flies so its shape tends to be distinctive in different birds. It is this distinctive shape that allows paleontologists that study birds to tell the different species apart. Other bird bones are equally distinct and also useful in making an accurate identification. When these bones are found associated in a single skeleton, it makes it possible for a paleontologist to be sure that an animal is correctly identified even if only a single bone is available.
Modern cormorants are fish eaters and it is most likely this was the case for the two fossil species at Hagerman. Their size difference would suggest that they ate different size fish. The fossil deposits at Hagerman include a wide variety of fish of various sizes. The exact diet of the two cormorants is unknown but perhaps someday another complete skeleton will be found that not only includes the bones of the bird but remains of its last meal in its ribcage as well.
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Brodkorb, P. 1958. Fossil birds from Idaho. Wilson Bulletin 70:237-242.
Marsh, O.C. 1870. Notice of some fossil birds, from the Cretaceous and Tertiary formations of the United States. American Journal of Science 49:205-217
Murray, B. G. Jr. 1970. A redescription of two Pliocene cormorants. The Condor 72(3):293-298
Wetmore, A. 1933. Pliocene bird remains from Idaho. Smithsonian Miscellaneous Collections 87(20):l-12.
This article originally appeared in The Fossil Record, Summer 1999