by Esther Lutz, East Central Illinois Extension Master Naturalist
When cold winds and chilling rains swoop down upon us each autumn, we grasp our collars close to our necks and appreciate the warmth of our cozy jackets, hats, and gloves. As those swirling leaves dance around us and then the snow begins to fall, the ability to take those insulating layers on and off is something we sure appreciate during the harsh winter conditions of east-central Illinois.
My daughter reminds me that her horse, Trooper, stabled at a local horse farm, is rapidly acquiring a fuzzy, winter coat. She frets over measuring him properly for the horse blanket she plans to purchase. This blanket will be a useful addition to her collection of horse "equipment" , acquired over time for his daily maintenance and care. After all, his body is naturally preparing itself for the months ahead, in much the same way that his wild ancestors did when winter descended upon the prairie. But being a domesticated animal in this day and age, his nutritional and shelter needs are met by human caretakers when the harsh outdoors begins to take its toll. A blanket with which to keep warm was certainly not something that his wild predecessors were able to enjoy. Yes, Trooper truly is a lucky fellow!
Creatures in the wild must prepare for the winter according to nature's way. Seeing our bird friends puffed up and huddled on the branches of backyard trees and shrubs in the chilly autumn rains, we can't help but marvel at their eventual ability to withstand the harsh conditions that lie ahead. Birds do possess a uniqueness that is unlike that of any other creature in the animal kingdom. What is so exceptional about them? They are the only animals on earth with feathers! And what an intricate and amazing thing a feather is!
Warmth, waterproofing, camouflage, flight, dramatic displays to attract a mate - these are all things that feathers provide. They not only streamline the birds' bodies to allow them to fly, but they also help to keep their skin dry and provide excellent insulation. There are many types of feathers, each with a specific purpose, and thinking of all of the ways that they are used to help birds survive can be a little daunting. Perhaps it's best to start thinking about the types of feathers, and how they're used to set birds apart from all other animals in the animal kingdom.
Flight feathers. Flight feathers are the ones that we most often picture in our minds when we think of the word "feather." They include the feathers of the tail and wings, and form the flight surfaces that enable a bird to fly. These larger feathers have a central quill and vanes. Barbs extend out from the quill, and from them extend hooklets and barbules that interlock together and give the feather its strength. Sometimes the barbules and hooks can become separated which can cause a "gap" in the feather. But nature provides a way for the birds to reattach the hooklets and barbules, as they can restore the integrity of the feather simply by running it through their beaks as they preen.
The outer wing feathers are comprised of three parts: the primary feathers which are longer and are at the forward tip of the wing, the secondaries, and the tertiaries which are located toward the back of the wing. Several layers of smaller coverts cover the top area of the wing feathers.
Contour feathers. The contour feathers cover the bird's body and create its smooth appearance. They protect the bird from the sun, rain, and snow, and are lightweight, yet somewhat stiff and strong.
Down feathers. The down feathers are small, soft, and fluffy, and are found underneath the contour feathers. They do not interlock together or have vanes like the larger feathers, and thus are perfect for trapping heat and keeping the bird warm. These are the types of feathers that give baby birds and chicks their adorable fuzzy appearance when very young, as well as providing great insulation on the bodies of adult birds. Other types of feathers cover the head and are used in courtship displays. These are called filoplumes, semiplumes, and bristleplumes. Some of these are also used to provide special sensory information.
Colors of feathers may vary greatly. Some birds will present a drab appearance called protective coloration which helps them to blend in discretely with their surroundings (often the case with females as they must sit in the nest for long periods incubating their eggs). Other birds will sport very vivid and brightly colored hues which serve to help them to attract a mate (as when males of a species compete for females), or as a quick and flashy way to tell other birds exactly who and what they are.
When feathers become worn and ragged, they will be lost and replaced through a process called molting. This usually occurs gradually, a few at a time each year, and often after the breeding season is over. Some species may molt more than once a year, as in the male American goldfinch whose summer yellow plumage is grown in February or March, while the more olive-drab winter feathers come in during the fall. In some species, the molting of the flight feathers occurs very rapidly and all at once, so they are unable to fly for a few weeks (ducks, swans, and pelicans). These birds often make their feather changes in secret hiding places so as to stay safely hidden from predators. But once the molt is over, every feather, vane and barbule is back in place, and the bird is good as new and ready to fly. Some species may even change their feather colors to match the season so that the feather-wearer may stay safely camouflaged all year round (arctic ptarmigan).
So how do birds use their feathers to keep warm? To put it simply, they fluff them up, and they grow more of them. Fluffing them up increases the dead-air space between the feathers and the skin. More dead-air means that more warm air is trapped and the bird can better retain its own body heat. Feathers provide even better insulation against the cold than mammalian hair. Together, they are the original "down jacket." And the more feathers a bird has, the more fluffing up it can do! (A chickadee, for example, may double the number of feathers it wears from summer to winter.) And when resting, a bird can tuck its head and feet into its feathers to conserve even more body heat, using them as a "blanket." There's just no end to what feathers can do!
Now that we know what a remarkable little piece of natural engineering the feather is, we needn't be quite so worried about our avian friends this winter. Oh, we can still help them out with food, water, and shelter, there will always be a need for those. But when it comes to winter coats, our bird friends are already pretty well-equipped. The feather truly is nature's masterpiece, and the birds are lucky to have it. As for my daughter's horse this winter, no feathers in the cards for him. I guess his fuzzy winter coat and that new horse blanket are just going to have to do.