Tag Archives | molt

Eclipse of the Ducks

Mallard Drake in Eclipse Plumage

Mallard Drake in Eclipse Plumage

When most people hear the term “eclipse” they think lunar or solar. But those familiar with waterfowl understand the term might refer to the feathers, or plumage, of a duck or goose.

Mallard Female

Mallard Female

All birds molt, a process of dropping old feathers and growing new ones. The new feathers keep the birds in good shape for flying, keeping warm, and sometimes for breeding showiness. By the end of summer the bright feathers of spring might be difficult to recognize. Many birds molt in the fall to replace worn plumage, and then again in spring to acquire their most alluring outfits.

Mallard Pair

Mallard Pair in Breeding Plumage

But waterfowl—ducks and geese—choose their mates earlier than songbirds. Ducks usually pair up by late fall, and cannot wait until spring to dress up. Male ducks, in particular, have gorgeous plumage, but in late summer all the males seem to disappear. The Sacramento River gains a steady supply of feathers floating downstream, and no male ducks are to be seen. The beautiful shining green heads of mallards vanish. The ornate wood ducks and brilliant male mergansers can’t be seen anywhere. Suddenly there seem to be many female ducks along the river, but no colorful males of these common year-round species.

Mallard Drakes in Eclipse Plumage

Mallard Drakes in Eclipse Plumage

There’s a scientific reason. Most birds lose a few feathers at a time, replacing them piecemeal without seriously disrupting their lifestyle. But ducks shed all of their outer feathers when they molt, including their wing feathers. For a few weeks, they become flightless. Males acquire the same camouflage as the females, a useful protection while they cannot fly. An observer can distinguish a male mallard at this time only by his slightly larger body and large, yellow bill, in contrast to her orange and black bill. Males at this hapless stage tend to gather in small groups and skulk along shores with reeds and grasses, laying low until new flight feathers develop. After those new wing feathers grow back the males enter a second molt into their bright breeding plumage. The second molt is less severe, and the ducks retain their ability to fly and escape from predators. All of this happens in timely fashion—in the fall, just before the duck dating season opens.

Wood Duck Pair

Wood Duck Pair in Breeding Plumage

Female mallards, wood ducks, and mergansers are always attired in camouflage, so they only molt once—but again, it is in time to have fresh feathers for understated attractiveness when the males come looking.

Geese also molt in the fall, but they usually mate for life, and seem to dress for long-term health and beauty rather than for just a brief courting period. They do not molt all their wing feathers at once, so, although briefly disheveled, they retain the ability to fly.

Wood Duck Drake Preening

Wood Duck Drake Preening

Ducks and geese can often be seen preening their new feathers. They have oil glands on their rumps, which supply the waterproofing that they spread over their sleek contour feathers. The feathers have small barbs that lock their parts together, and combing them helps keep the birds smooth, warm, and attractive. Waterfowl instinctively know how important their feathers are, and do the work to maintain them.

Wood Duck Pair in Eclipse Plumage

Wood Duck Pair in Eclipse Plumage

Webster defines “eclipse” as to obscure, leave out or fail. He discusses the partial or total obscuring of one celestial body by another, making one seem less brilliant, but he makes no mention of the less brilliant plumage of male ducks in the fall. Ornithologists, however, have studied the annual phenomenon extensively. Eclipse plumage allows ducks to quickly molt into fresh breeding feathers. Understanding it solves the mystery of the disappearance of the male ducks.

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Birds Pull Out Their Winter Coats

Bald Eagle Juvenile

Bald Eagle Juvenile photo courtesy David Bogener

What’s up with our backyard birds? Where are they?

You may have seen them over the last months busily carrying load after load of insects to feed their ravenous nestlings, then being raucously pursued by fledglings demanding yet more food – sometimes with two or even three batches of babies through the season. All this effort has taken a toll on the adult birds’ feathers and now, despite the daily care they have taken preening and cleaning them, the feathers are worn out. The birds are lying low during their molt – the annual or twice yearly loss and regrowth of feathers done by most songbirds. But don’t expect to catch a glimpse of bald birds – each worn feather becomes loosened in its socket and is pushed out by the growth of a new feather.

The process takes from 5 to 12 weeks for songbirds, after which some will appear in winter plumage quite different from the bold patterns some males sport in summer. For example, American Goldfinch males are bright canary yellow with bold black accents during the breeding season, but become a quieter butterscotch color, much like females and juveniles, in their winter garb. Similarly, you may see a male Western Tanager that has lost his gaudy orange head feathers and exchanged them to the muted gray of a female before starting the long, dangerous migration to Costa Rica for the winter.

Bald Eagle 4 Year Old

Bald Eagle Sub-Adult photo courtesy David Bogener

Other groups of birds go about the molt differently. Ducks, geese and some other water birds go through a rapid “synchronous molt”. They change their feathers quickly in a period as short as two weeks which renders them flightless for that period. This seems like a risky business – but researchers have deduced that since these birds are heavy relative to their wing surfaces, losing a few feathers at a time would seriously hamper flying ability, so they get it over with as quickly as possible and minimize the length of time that they are especially vulnerable to predators.

Raptors (eagles, hawks, falcons and their kin) “make their living” on the wing and can’t afford to suffer periods of impaired flying abilities. These birds may take as long as two years to complete a molt. The loss of flight feathers must be symmetrical or flying would be skewed. A woman who raised an owl that could not be released into the wild observed this in action. She reported that her feathered friend pulled a loose wing feather out and gave it to her, then immediately removed the corresponding feather from the other wing.

Bald Eagle Adult

Bald Eagle Adult photo courtesy David Bogener

To give young Turkey Vultures a good start, they don’t molt their flight feathers until they are two years old. The vultures soaring over minus a couple feathers are almost certainly adults.

In most birds, tail feather replacement is from the center of the tail toward the outer edge. Woodpeckers reverse this for a very good reason. Watch closely the next time you see one ratcheting up a tree and you will see that it braces itself firmly using its stiff tail feathers. The key for this is an inner pair of long feathers. Those are retained until the outer tail feathers have been replaced with fresh, strong vanes, keeping the woodpecker able to fully function searching for insects in the bark.

You may find a single feather in your yard – evidence that one of “your” birds has cast it off for a brand new set of feathers to get it through the winter or prepare it to head off to winter habitat in Mexico, Central America or South America. Enjoy the memento!

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