Have you ever seen a bird missing a lot of feathers? It’s called molting and the end of summer is when most birds go into a molting cycle.
Molting is the process of regenerating feathers. Feathers must be replaced as they get damaged from normal wear and tear. Feathers are critical for aerodynamics and insulation from the weather.
Most birds will replace all their feathers at least once a year. They make sure to not do this during breeding season so they look their finest. They also don’t molt during migration times as they need all their feathers for the long flights most birds endure during migration.
Molting takes a lot of the bird’s energy as it must grow all new feathers during a relatively short time. During the end of summer when breeding is complete, most backyard birds will start the process of molting. Molting times vary depending on the type of bird but most last 5 to 12 weeks.
Some varieties of smaller birds get rid of the bright breeding colored plumage and replace them with the dull coloring for winter. Come early spring they will go through the cycle again to get those bright colors back just in time to impress their mate.
A male goldfinch with breeding plumage 
A male goldfinch in winter plumage
While larger birds do partial molts throughout the year because it takes longer to grow their long feathers, their molting is almost a year-round process.
Molting can also be used to determine a bird’s age as juvenile birds will have different feather coloring and patterns than their adult counterparts. Juveniles usually have to go through a molting cycle several times before achieving their adult plumage. For instance, a bald eagle takes four years before they have that majestic look.
Fledgling bald eagle on ground 
Juvenile 2nd year bald eagle 
A 3rd year bald eagle with mostly adult feathers 
Four-year-old bald eagle with adult feathers 
Bald eagle in flight
Feathers are composed of keratin, the same material as human hair and nails but while our hair and nails continuously grow, bird feathers only grow one time. Once feathers are damaged they need to be replaced and that is the molting process.
So next time you see a bird that is looking a little rough around the edges, just know that it is doing it’s best to look good. And if it’s your backyard buddies then go ahead a put out a little extra seeds as it takes a lot of energy to grow all those feathers at once.
