These letters relate to natural history and birds.

The primary correspondence (ca. 65 letters) is with William Cooper (1798-1864) on Bonaparte's publications, especially "American Ornithology" and "Observations on the Nomenclature of Wilson's Ornithology," but also included are many references to American and European men of science and learned societies. There are also letters to Isidore Geoffroy Saint-Hilaire, George Robert Gray, Titian Ramsay Peale, and Wilhelm P. S. Rüppell.