The feather, because of its relative simplicity, its availability, and its response to different physiological conditions that can be regulated quantitatively, is a valuable instrument for studies in various biological problems.
"Feather Morphology In Biological Research,"
Iowa State University Veterinarian: Vol. 10
, Article 4.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol10/iss1/4