John Wesley Powell & Dale Birkenholz Natural History Collections The bird and mammal collections total over 6,000 specimens representing 560 species and 120 families, and date back to 1867. The bulk of the collections is from Illinois and the United States, with holdings also from Africa, India, Europe, and South America. We prepare salvaged birds and mammals into scientific study skins, and save stomach contents, skeletons, and frozen tissues (for DNA).