Bird Molting: Why Birds Molt and How to Spot It

Feather refresh in progress! Learn about bird molting and why the color change is more obvious on some molting birds than others.

Why Do Birds Molt Their Feathers?

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American goldfinch in nonbreeding plumage.

Birds are the only living species with feathers, so it only makes sense that feathers have some one-of-a-kind features. The structure of feathers is strong and durable, yet they are lightweight and flexible. And although feathers do wear out, birds molt them by regrowing new ones. Often this natural process goes unnoticed, but bird molting patterns are fascinating.

“Molt is my favorite,” says Annie Lindsay. As the bird banding program manager at Carnegie Museum of Natural History’s Powdermill Nature Reserve in southwestern Pennsylvania, she gets an up-close look at the process on thousands of birds annually.

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Bird Feather Types

Juvenile Bald Eagle 56a9326 CopyChristine Haines
Based on feather patterns, this bald eagle is less than 4 years old.

Not all feathers serve the same purpose. According to Annie, specific feathers are essential for everything from flight to keeping birds warm. “Flight feathers on the wings and tails are longer and somewhat stiffer,” she says. The shape of the wing provides lift, and tails serve as rudders for birds. Body feathers, including down and contour feathers, help birds regulate their temperatures.

“Birds puff up their feathers to conserve heat,” Annie says. “It’s like when we get goose bumps on our arms.”

Another specialized feather type is found along the beaks of flycatchers and other insect eaters. These rictal bristles look like whiskers and likely have a sensory function, Annie says.

Bald Eagle Mg 7354 Copy HighresChristine Haines
Eagles molt some flight feathers after breeding season. The National Eagle Repository collects feathers and then distributes them to permit-holding Native Americans who use them in traditional ceremonies.

Feathers can be extremely fancy or ridiculously plain. Either way, they are also a way for birds to communicate with one another.

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Bird Molting Patterns

Mallard Drake DuckRichard Buquoi
This male mallard has already replaced its flight feathers and is coming into its breeding plumage.

Variations of bird molting scenarios are endlessly complex within species. But Annie provided a glimpse into the general basics for songbird molts. After hatching, young birds grow juvenile plumage.

“Since all of the feathers are growing in at the same time, not as many resources can be used per feather,” Annie says. “These juvenile feathers are of lower quality.”

Young birds then replace their juvenile plumage with feathers in better condition. Most species will replace all feathers on their bodies almost a year later.

For bird-watchers, some species can pose tricky identifications because younger birds don’t always look like adults. Young red-headed woodpeckers have brown heads, for example. Similarly, young white-crowned sparrows could be referred to as brown-crowned sparrows.

bird molting Tanager Summer 1yr Malevd Masl1220Steve and Dave Maslowski
This patchy summer tanager is 1 year old; the next time it molts, it will wind up with all red feathers.

The annual, or in some cases biannual, molt cycles that species follow allow “feathers to be replaced here and there, so more energy is allocated to each individual feather,” Annie says.

The molting process is relatively quick for North American fliers. “Molt can happen in a matter of a few weeks as birds are preparing for migration or breeding,” Annie says, “Although in the tropics where conditions are relatively uniform, molt can be much slower.”

Summer TanagerGail Buquoi
Adult male summer tanager in breeding plumage.

For some species, including tanagers and buntings, new feathers help them look their finest as they try to attract mates in the spring. This could still be the case for birds that don’t undergo drastic color changes.

“Even if we don’t see the differences, birds can see in the UV part of the spectrum, so we might see all brown feathers, while birds might be able to see the contrast between old and new feathers,” Annie says.

Does Molting Hurt Birds?

During a normal molt, “the feathers are ready to drop and are falling out naturally,” Annie says. Feathers are dead tissues, so it isn’t painful if they are broken or when they fall out during molt, but plucking them out could potentially cause some discomfort. Frayed, damaged or broken feathers aren’t replaced, but removed ones, such as when a bird narrowly escapes a predator, will have an impact. “Any time birds lose a feather, replacing it has energetic consequences,” Annie says.

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Molting Ducks Are Flightless Birds

During molt, ducks join the ranks of flightless birds. Many waterfowl species replace all their flight feathers at once, which keeps them grounded for a few weeks. Males take on an eclipse plumage and are more camouflaged, like females, during this summer transition.

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Unique Molt Patterns

Goldfinchamer.sunflowers Yl5t8721Steve and Dave Maslowski
American goldfinches are well-known molting birds. Their appearance changes throughout the year. This bird is in winter plumage.

From piebald patterns to entirely bald heads, molt makes for some interesting-looking birds. American goldfinches are a great example to observe molt.

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Early spring molt

“Brownish in the winter, as they get ready for breeding season, you can watch the transition and see how mottled they look on their bodies,” Annie says. Then the process repeats in the fall as birds molt into their winter feathers.

Goldfinchameri.apple.tree Cd 3mas2961kSteve and Dave Maslowski
American goldfinch in late spring and summer breeding plumage.

This blotchy pattern on the body is also evident on tanagers and bobolinks during certain times of year.

For cardinals and blue jays, bird molting is generally a subtle affair. They don’t look much different between seasons as feathers are swapped out with similar-looking replacements.

molting cardinalCourtesy Cherie Souhrada
This mystery bird with the odd hairdo is an adult male cardinal. The bald look is sometimes caused by environmental factors like nutritional deficiencies or feather mites, but it’s most commonly the result of molting.

But sometimes molt is impossible to miss, as some individual birds are prone to an “unfortunate pattern of molt baldness,” as Annie puts it. Nothing is wrong with these birds—they’ve just lost all the feathers on their heads simultaneously.

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Ken Keffer
Ken Keffer has a degree in wildlife biology and is an award-winning environmental educator and author. His career has been spent highlighting the importance of nature and encouraging people to explore the outdoors. Ken is the current president of the Outdoor Writers Association of America. He recently put down roots in Bloomington, Indiana, where he and his wife Heather Ray own a backyard bird feeding nature shop. His work can be found at www.kenkeffer.net.
Kirsten Schrader
Kirsten has more than 15 years of experience writing and editing birding and gardening content. As content director of Birds & Blooms, she leads the team of editors and freelance writers sharing tried-and-true advice for nature enthusiasts who love to garden and feed birds in their backyards. Since joining Birds & Blooms 17 years ago, Kirsten has held roles in digital and print, editing direct-to-consumer books, running as many as five magazines at a time, and managing special interest publications. Kirsten has traveled to see amazing North American birds and attended various festivals, including the Sedona Hummingbird Festival, the Rio Grande Bird Festival, The Biggest Week in American Birding Festival, and the Cape May Spring Festival. She has also witnessed the epic sandhill crane migration while on a photography workshop trip to Colorado. Kirsten has participated in several GardenComm and Outdoor Writers Association of America annual conferences and is a member of the Wisconsin Society for Ornithology. When she's not researching, writing, and editing all things birding and gardening, Kirsten is enjoying the outdoors with her nature-loving family. She and her husband are slowly chipping away at making their small acreage the backyard of their dreams.