Why Some Birds Molt Faster Than Others

Every year birds replace wing feathers crucial for flight, but how long this process takes can vary.

This audio story is brought to you by BirdNote, a partner of The National Audubon Society. BirdNote episodes air daily on public radio stations nationwide.


This is BirdNote.

Feathers are miraculous structures. Especially the long, strong feathers of a bird’s wings and tail that make flight itself possible. But after about a year, constant use and exposure to the elements mean they have to be replaced. So how do you replace the roughly 20 feathers in each wing that are essential to flight, without becoming earthbound?

Many birds molt a few flight feathers at a time, wait until new ones grow in, molt another few, and so on. Usually the same feathers on each wing at the same time, symmetrically. So in summer, a raven that’s molting might look a little ragged in the same part of each wing. For ravens, a molt can take up to six months. For smaller birds, closer to two. But — crucially — they can still fly. 

Waterbirds like ducks and loons, though, are too heavy to fly with even a few feathers missing. So they molt all their flight feathers at once, becoming earthbound and especially vulnerable to predators for a month or more. During this time they stay in or very close to the water and out of harm’s way. Until their full suite of feathers has been completely restored. 

For BirdNote I’m Michael Stein.



Written by Bob Sundstrom

Producer: John Kessler

Executive Producer: Dominic Black

Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. 
Common Raven call [137574] recorded by Gerrit Vyn
‘Sonata I’ by John Cage performed by Maro Ajemian from ‘Sonatas and Interludes for Prepared Piano’ - El Records 
BirdNote’s theme music was composed and played by Nancy Rumbel and John Kessler.

© 2015 Tune In to Nature.org

August 2017    ID #: molt-03-2015-08-10 molt-03