One of the most important of Academy collections, with more than 2,400 documented sets of eggs and nests, comprising 440 species of North American birds. Since the 1985 publication of Kiff and Hough's Inventory of Bird Egg Collections of North America, the Academy's catalogued holdings have almost doubled. Included are Passenger Pigeon eggs (the species is now extinct), the first documented egg of the Kittlitz' Murrelet (rarely found in Illinois), and other Midwestern specimens. Six hundred fifty sets are from Illinois, and many are accompanied by extensive field notes.