Haliaeetus leucocephalus, the bald eagle, with its white head and tail and brown body is easily recognizable as the national emblem of the United States. The bald eagle is a large raptorial bird but typically prefers to scavange or steal prey items from other species whenever possible. A large portion of its diet is composed of fish, although it may also eat small mammals, birds, or reptiles (Buehler, 2000).
The distribution of bald eagles ranges over most of North America, and it is most often seen near aquatic habitats. There was an abundance of bald eagles in the 19th and early 20th centuries; however, due to overhunting and habitat loss their numbers dropped significantly. Although hunting of H. leucocephalus stopped when the Bald Eagle Protection Act was enacted in 1940, their numbers dropped further because of the use of pesticides including DDT. Since the banning of the use of DDT, the number of bald eagles has increased steadily (Buehler, 2000).
Falconiformes which traditionally includes Accipitridae (eagles, hawks, and kites), Falconidae (falcons), Cathartidae (New World vultures; see Coragyps atratus), and Sagittariidae (secretary bird), may be paraphyletic with respect to Strigidae (owls; see Athene cunicularia and Tyto alba) (Mayr and Clarke, 2003; Mayr et al., 2003; Cracraft, 1988). The taxon Accipitridae, however, is most closely related to Falconidae. This relationship is support by several morphological characters, vomers vestigial or absent, a basipterygoid articulation absent in the adult, the caudal margin of the sternum has two notches/fenestrae, the distal end of the ulna has a marked depressio radialis, and the musculus femorotibialis externus does not have a distal head (Mayr and Clarke, 2003).
About the Species
This specimen (TMM M-7260) was collected by Federal Game Warden Don Krieble 30 miles south east of Lubbock, Texas. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Timothy Rowe of the Department of Geological Sciences, The University of Texas at Austin. Funding for scanning was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Rowe.
About this Specimen
The specimen was scanned by Matthew Colbert on 26 January 2004 along the coronal axis for a total of 751 slices, each slice 0.169 mm thick with an interslice spacing of 0.169 mm.
Baumel, J. J., A. S. King, J. E. Breazile, H. E. Evans, and J. C. Vanden Berge (eds.). 1993. Handbook of Avian Anatomy: Nomina Anatomica Avium, Second Edition. Publication of the Nuttall Ornithological Club, number 23. Nuttall Ornithological Club, Cambridge, Massachusetts, 779 pp.
Buehler, D. A. 2000. Bald Eagle. The Birds of North America 506:1-40.
Cracraft, J. 1988. The major clades of birds; pp. 339-361 in M. J. Benton (ed.), The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, and Birds, Systematics Association Special Volume No. 35A. Clarendon Press, Oxford.
Mayr, G., and J. Clarke. 2003. The deep divergences of neornithine birds: a phylogenetic analysis of morphological characters. Cladistics 19:527-553.
Mayr, G., A. Manegold, and U. S. Johansson. 2003. Monophyletic groups within 'higher land birds' -- comparison of morphological and molecular data. Journal of Zoological Systematics and Evolutionary Research 41:233-248.
A species profile for the Bald eagle on the U.S. Fish & Wildlife website.
Haliaeetus leucocephalus on Animal Diversity Web (University of Michigan Museum of Zoology)
Haliaeetus leucocephalus on Calphotos.