Bird Molting: Why Birds Molt and How to Spot It
Now you see them, now you don't! Discover why goldfinches and other backyard birds molt and change color in the fall and how to identify molting birds.
As summer slips into fall and the weather cools down, swimsuits and shorts are swapped for sweaters and scarves. Birds also change their wardrobes with the seasons. To maintain their feathers for flight and keep them water resistant and insulating, birds regularly replace their plumage with new feathers in the process called bird molting. Many species look the same 365 days of the year, but some look so different in fall that they are challenging to identify.
The Basics of Bird Molting
Take the American goldfinch, for example. All summer, glowing yellow male American goldfinches nibble at your feeder, and then one fall day there’s not a bright lemon-colored songbird to be found. In fact, the goldfinches are still around and coming to feeders. They just look different—drab and dull. The color changes of the female American goldfinch are subtle, but the male is all drama. He transitions from blazing yellow to a much duller yellow-brown, making him look more like the female.
His feathers aren’t actually changing color. Instead, the bird gradually replaces all the feathers in a process called molting. Over the span of a few weeks, old feathers slowly drop out and new ones grow in. If you spot the male goldfinch in the middle of molting, he’ll have patches of yellow and brown. But once he’s decked out in his autumn garb, you’d never guess he was once bright yellow.
Examples of Birds That Molt
Bird molting isn’t unique to goldfinches. As a rule, any healthy wild songbird replaces its feathers at least once a year. Late summer to fall is the most common time for this to happen, but in many cases it’s not too noticeable. A male cardinal, for example, replaces old red feathers with new red feathers, so he looks freshened up but otherwise unchanged. In some cases, particularly blue jays, cardinals and a few blackbirds, the head molt can happen all at once, resulting in very strange bald-looking birds.
Some birds molt into a completely different plumage in fall. One bird that changes in a big way is the male scarlet tanager, which is scarlet for only half the year. In late summer, this species replaces all its feathers before migrating to South America in fall. The male plumage changes from brilliant red to dull yellowish-green, like the female’s. The same thing happens to the bobolink of meadows and hayfields. The male bobolink’s breeding plumage of black, yellow and white is replaced by a yellowish-brown sparrowlike pattern before he flies off to South America in fall. The male indigo bunting molts from an intense deep blue in spring and summer to mostly brown.
When Fledgling Birds Molt
A new challenge in late summer comes as young birds leave the nest, looking very different from their parents. Baby chipping sparrows are covered with dark streaks, while their parents have smooth gray chests and reddish caps. Fledgling robins and bluebirds are covered with spots at first but eventually lose them as they grow up. The majority of small birds, however, molt their body and head feathers soon after they become independent, quickly replacing their juvenile plumage. Within a month, they look recognizably similar to adults.
Once fall arrives, some young birds look very different. Cedar waxwings usually nest late in summer, so you might see streaky brown juveniles as late as November. Young red-headed woodpeckers have brown heads until late fall and occasionally through winter. While adult white-crowned sparrows are smooth gray and brown with sharp black and white head stripes, their kids have brown and tan stripes on their heads through their first fall and winter.
How to Identify Birds That Are Molting
The good news is that as tough as it can be to identify adults that change color or youngsters that look different from their parents, it’s not impossible. For starters, when you see an odd bird in fall, look beyond its colors and focus on its shape, size and actions. Even without bright hues, a male scarlet tanager is still a medium-size songbird with a thick bill that moves quietly through the foliage in tall trees. Although a young cedar waxwing has stripes on its chest, it’s still a crested bird that sits upright, eats berries and flies out to catch insects in midair. It’s also likely to be in a flock with other waxwings.
Another tried-and-true tip is to look closely at the wings and tail. On most birds, these don’t change as much as the head and body do. That male scarlet tanager may be mostly greenish yellow in autumn, but he still has black wings. The young cedar waxwing has a yellow band at the tip of its tail, just like the adults.
A good way to practice fall bird ID skills is to look at those American goldfinches again. The males lose their bold color, but they’re still tiny birds with thick, seed-crunching beaks. They’re still active and sociable, moving around in flocks, with a bouncy flight and short musical calls. They still have black wings with white or buff wing bars, and white spots on black tails. The bright gold color may be gone, but that goldfinch personality is always present.
Soon it’ll be spring again. Watch your feeders and you may witness a magical bird molting transformation as the goldfinches go from patchy brown and yellow on the way to a sparkling summer wardrobe.