)[2] From September 1955 to January 1956, Ficken worked as a research assistant in the Bacteriology Laboratory at the University of Oklahoma.
In 1960, she earned her Ph.D. in zoology from Cornell with her dissertation titled Behavior of the American Redstart, Setophaga ruticilla (Linnaeus).
[1] Ficken's research interests included animal communication with a focus on the calls and social behavior of birds, especially penguins, hummingbirds and North American songbirds, on whose vocalizations she carried out several long studies.
After retiring from the university in 1999, she continued pursuing her own scientific studies, and in 2003 she was made Professor Emerita at the Department of Life Sciences at UWM.
In his orchestral work, The Chickadee Symphony, composer Craig Thomas Naylor, added the following notation to his score's title page: "Dedicated to Millicent ('Penny') Ficken."
In his notes to the conductor, Naylor credited Ficken with introducing him to the Black-capped Chickadee and their "remarkably complex" vocalizations.