Bird collections are curated repositories of scientific specimens consisting of birds and their parts. They are a research resource for ornithology, the science of birds, and for other scientific disciplines in which information about birds is useful. These collections are archives of avian diversity and serve the diverse needs of scientific researchers, artists, and educators. Collections may include a variety of preparation types emphasizing preservation of feathers, skeletons, soft tissues, or (increasingly) some combination thereof. Modern collections range in size from small teaching collections, such as one might find at a nature reserve visitor center or small college, to large research collections of the world's major natural history museums, the largest of which contain hundreds of thousands of specimens. Bird collections function much like libraries, with specimens arranged in drawers and cabinets in taxonomic order, curated by scientists who oversee the maintenance, use, and growth of collections and make them available for study through visits or loans.