Overview Crawford Hallock Greenewalt (1902-1993) was a chemical engineer and the President of the DuPont Company from 1948 to 1962. He had a passion for the natural sciences, and combined his love of ornithology with photography. He was especially known for his high speed photographs of hummingbirds. His ornithological interests included bird songs, the radiance of hummingbird feathers and the evolution of shapes and sizes of birds in relation to their flight abilities. The Crawford H. Greenewalt...