[2] One of her most notable career achievements was becoming a Secretary at the Royal Ontario Museum in which she worked in the palaeontology department.
[3][1] 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.
While in Brazil, she discovered the Avifauna, which eventually led to two papers to be published in The Auk and the Wilson Bulletin in 1954, and a monograph on Brazilian birds (1957).
[2] In 1958, she was made an "Elective member" [clarification needed] of the AOU as a follow-up to her notoriety from her publishings.