H.J. Ruiz – Avian101

Molting

A feather is a “dead” structure, somewhat analogous to hair or nails in humans. The hardness of a feather is caused by the formation of the protein keratin. Since feathers cannot heal themselves when damaged, they have to be completely replaced. The replacement of all or part of the feathers is called a molt. Molts produce feathers that match the age and sex of the bird, and sometimes the season.

Molting occurs in response to a mixture of hormonal changes brought about by seasonal changes. The entire process is complex and many questions remain regarding how the process is controlled. A basic understanding of molting patterns can, however, be a useful aid in identifying many species and in determining their age.

There are two kinds of molts with different degrees of feather replacement.

• In a complete molt all feathers are replaced.
• In a partial molt only some feathers are replaced.

Damaged feathers are replaced during a molt. A feather that has been lost completely is replaced immediately.

How often do birds molt? This varies by species.

I brought you a series of pictures I shot of a male Northern Cardinal in my backyard. It’s the perfect example of molting.

Northern Cardinal full plumage

Text excerpts © the Cornell Lab of Ornithology – All photographs © H.J. Ruiz – Avian 101