These are duck specimens in the natural history display at the 1876 Centennial Exposition in Philadelphia. It is part of several large collections (containing hundreds of photographs) recently uploaded to Flickr by the Smithsonian Institution. Many photographs (such as this collection of cyanotypes) illustrate objects from the collections. Others document life around D.C., such as this aerial view from 1932 and this three-wheeled postal motorcycle. And then there are many portraits of artists and scientists, such as Charles Darwin and Asher Durand.Since these are federal government collections, and many date to the 19th century, the images in the photostream are in the public domain. So this could be a good resource for bloggers looking for images.