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Featherfall.

As many birders know, early August can be the doldrums. The breeding season has ended. and for the most part, fall migration has yet to begin. The heat of midday stifles bird movement. and yet, the signature feature of birds is all around us--in the form of feathers--and their presence became clear to me on a recent, early August stroll through a wooded preserve near my home.

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Hiking on a path through a swampy area I watched as a brilliant red tupelo leaf gently rocked earthward in shallow, U-shaped flutters, touching down on the wooded path a few steps in front of me. A small feather lying next to the fallen leaf caught my attention. I picked it up to inspect it and quickly realized, because of its extreme asymmetry and color, that it was a primary flight feather from a blue jay's right wing. The main flight feathers, known as primaries, are typically asymmetrical to serve as airfoils. They provide a small amount of lift to supplement the lift provided by the curved wings, a bird's primary airfoils.

Ten feet further along and on the other side of the path, I spotted another feather, this one with black and white flecking and a pointed tip. I picked it up and brushed it against my palm--it was surprisingly stiff, and l realized I was holding a woodpecker's tail feather. Woodpeckers use their tails to brace their bodies when they feed upright along tree trunks, so it's not surprising to learn that their tail feathers are stiff and strong.

Then, diagonally across the path, 1 spied another tail feather, though not nearly as stiff as the woodpecker's. This one was black, longer, and ragged, and until recently belonged to a common grackle. By the time my hike had ended, I'd found eleven feathers belonging to five different species.

Why the sudden presence of so many fallen feathers? It all stems from wear and tear. Over time, feathers are exposed to harsh elements like sunlight, wind and rain; they are abraded by rubbing against vegetation and other objects, and are ruffled and preened countless times each day. Collectively, these actions literally wear feathers down; consequently, they must be periodically replaced through a process known as molting.

Building nests, feeding young, and migrating all place significant energy demands on birds. So, taking advantage of the window of time after the nesting season but preceding fall migration, many birds molt all of their worn feathers and replace them with a fresh set in late summer. This common molting pattern occurs in birds that look the same all year round, such as robins, blue jays, and birds of prey. Birds that change their garb between breeding and non-breeding seasons, such as warblers, tanagers, and shorebirds, exhibit a second partial molt in the spring to don their beautiful breeding colors.

Molting is generally a gradual affair, with birds losing a few feathers at a time. it's not unusual to see a flying crow or hawk missing the same primary flight feather from each wing. In some waterfowl however, molting is a more compressed event with most ducks losing all their flight feathers at the same time, rendering them flightless for a short period each summer. This synchronous molt coincides with loss of their breeding colors, so they are also less conspicuous. The drab coloration is termed the "eclipse" plumage, since the pretty plumage has been eclipsed by a dull feather coat. The resplendent breeding colors, which make ducks such an attractive group, return with the new flight feathers that grow in during the fall.

A bird's flight feathers are comprised of the wing and tail feathers, technically known as remiges and rectrices. While these are the largest and most conspicuous feathers birds possess, birds also have other types of feathers that provide important functions. Down feathers, for example, are hidden beneath the surface and provide warmth, while contour feathers at the surface provide color, camouflage, and aerodynamic benefits. Some birds like flycatchers, goatsuckers, and woodpeckers have bristles, specialized feathers on the face which are thought to help protect the eyes during food capture. Birds also possess filoplumes, feathers with a unique function. The base of these feathers are rich in nerve endings, and are very sensitive. If a filoplume is out of order, making it very likely adjacent contour feathers are too, the bird knows it and will preen, using oil from a gland located at the base of the tail, to put the feathers back in order.

Contemplating the blue jay feather, I experienced magic--by a deft wave of my hand I changed its color! First, I held the feather so that my body was between the feather and the sun, producing a feather with a bold cobalt blue color. Then I positioned the feather between the sun and myself and the cobalt blue faded to a dull grayish-brown, the "real" color of a blue jay. How to explain this spectral sleight of hand?

To find out, we must first understand the factors responsible for feather color. Many blues and greens found in plumage are known as structural colors and owe their existence not to pigments but to the way light is reflected by the feather's microscopic structure. Change the angle between the feather and the light source and you can change its color. In the case of the blue jay feather, all other wavelengths of light that make up the visual spectrum are absorbed by the feather except blue, which is reflected back to your eye. A blue jay, then, could be considered to be "really" a mousy gray brown! Iridescent colors such as the head feathers of greater scaup, a hummingbird's throat patch (gorget), and the contour feathers of a grackle, all work in a similar way.

In contrast, feathers colored black, brown, yellow and red are suffused with pigments of those colors. A cardinal, for example, has feathers containing red pigments. If you attempt the same trick with a pigmented feather, it will only appear to be a lighter or darker tint of the same color; it will not look as if it changed color, as does a blue jay feather.

y sudden fascination with feathers didn't end there. The last feather I found that day was a crow flight feather, in remarkably good shape with little abrasion. This is not surprising, since black feathers, with greater amounts of melanin, wear more slowly than do lighter feathers. You may have noticed that many bird species' wing tips are black. This stands to reason, as wing tips are subject to the greatest physical stress. Herring gulls and snow geese are but two of many examples.

Holding the feather in my hand, I gently tugged along the margin of the wider of the two vanes, but it didn't separate easily, because of its structure. Hundreds of parallel barbs extend from the middle rachis of a typical flight feather. In turn, hundreds of barbules project from each barb. Barbules have microscopic hooks that snag the barbules on adjacent barbs. Interestingly, this arrangement provides the feather with great rigidity and flexibility, all at the same time.

To be honest, I didn't expect to make much of a connection with birds during this hike on a hot, humid day. But I came away from this contemplative walk with a renewed interest in feathers; yet another reason why birds fill my world with fascination, wonder and awe.

John Turner is a freelance writer and the author of two books, "Exploring the Other Island," a seasonal guide to Long Island, and "Waylon's Water Drop," a children's book on the water cycle.
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Title Annotation:bird feathers
Author:Turner, John L.
Publication:New York State Conservationist
Date:Aug 1, 2004
Words:1272
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