Mersom started the William B. Mershon and Company in Saginaw that manufactured bandsaw blades which his father was attributed with inventing.
For two years he was a state forester and he was an associate life member of the American Ornithologists' Union and here his interests enabled him to gather together the material from a number of sources to publish a volume on the passenger pigeon in 1907.
The book on the passenger pigeon was published several years after the last of this once endemic bird was last killed (in 1900) and before the last died in captivity in an American zoo.
He wrote in his 1927 autobiographical memoir, “Recollections of My Fifty Years Hunting and Fishing,” fate intervened when he received his first gun – a sixteen gauge muzzle loader – around the age of ten.
Mershon had married Catherine Morse from Detroit in 1889, and they had three sons, William Briggs, Edward Lowery, and John Morle, and two daughters.