The collection began with the donation of study skins, (dated between 1875 to 1925) from the private collections of J.H. Sage and W.E. Treat, and emphasizes the fauna of Connecticut and the northeastern U.S. There are also specimens from the Aleutian islands, Paraguay, and other areas. The study skin collection holds more Connecticut specimens than any other in the world. Particularly noteworthy are the raptors. In addition, the collection includes approximately 1,000 bird skeletons (ranked 49th in size internationally in 1983), over 1,000 fluid preserved bird specimens (ranked 25th in size internationally in 1983), one of the few known feather collections in the world (from the work of emeritus Prof. Alan Brush), and a valuable collection of nests and eggs from the turn of the century.