Roosevelt called often at my office to discuss the broad country we both loved, and we came to know each other extremely well. Though chiefly interested in big game and its hunting, and telling interestingly of events that had occurred on his hunting trips, Roosevelt enjoyed hearing of the birds, the small mammals and the incidents of travel of early expeditions on which I had gone. He was always fond of natural history, having begun, as so many boys have done, with birds; but as he saw more and more of outdoor life his interest in the subject broadened and later it became a passion with him.
– George Grinnell
Excerpt from American Sportsmen and the Origins of Conservation by John F. Reiger.