During his teen years and early twenties, he worked as a farmhand and ranch hand.
[3] For two years from 1920 to 1922 he served in the central United States as a missionary for the LDS Church.
Jay Norwood "Ding" Darling, the bureau's director, gave Cottam much of the responsibility for duck hunting regulations.
[5] During the early years of his federal government career, he was also a part-time student at George Washington University, where he graduated in 1936 with a Ph.D.[3] His Ph.D. thesis Food habits of North American diving ducks was the basis for a 140-page publication in 1939 by the United States Department of Agriculture.
He worked with her until 1952, when she retired from government service to write full time, and remained a close friend until she died in 1964.
[8] In her 1962 book Silent Spring, she cited his investigations of the harmful effects of insecticides.
[5] He accumulated a comprehensive library of ornithological journals and textooks on American for the use of students at the Welder Wildlife Refuge.
[5] In 1962 he received both the Frances K. Hutchinson Medal of the Garden Club of America[13] and the Paul Bartsch Award of the Audubon Naturalist Society.