(noun) A type of protein common in organic, biological structures. In birds, the beta-keratin form of this protein is a major component of bills, feathers and talons. It is lightweight and strong, though it does wear down with use and is regenerated throughout a bird's life. The bill and talons grow continually, while worn feathers are replaced through regular molting.
In some birds, genetic abnormalities may cause improperly aligned features that could show excessive keratin growth, such as elongated bills or talons. When this occurs, birds may have difficulty feeding or performing other necessary functions because of abnormally shaped bills and talons.
Photo – Flamingo Feathers © Greg Livaudais