One of her most notable career achievements was becoming a
Secretary at the
Royal Ontario Museum in which she worked in the
palaeontology department. After Mitchell's position at the
Royal Ontario Museum she became a volunteer with the task of helping create and write the "
Passenger Pigeon Inquiry" which later became "The Passenger Pigeon in Ontario" (1935). Her volunteer work in ornithology lead to Mitchell to attain the title of the first woman research affiliate in any natural history museum in Canada. She was also a member of the
American Ornithologists' Union (AOU) in 1928 and the
Wilson Ornithological Society in 1933, although at the time was not allowed to join the all-male birds clubs in the
Toronto Area. == Research and findings ==