By BILL CHAISSON
By Bill Chaisson
Anyone who has ever plucked a chicken knows how much smaller the birds look after their feathers are stripped from them. A significant part of the bulk of a bird, but not its weight, is in its feathers. Most birds are not very heavy, ranging in weight from a few grams to a few ounces. They are small descendants of much larger animals, the dinosaurs, that evolved homeothermy — being warm-blooded — independently from mammals. The keys to keeping warm are their feathers and their warm-bloodedness.
Feathers operate on principle similar to that of storm windows; a layer of air between the outside and the inside keeps the inside warm. Birds have two kinds of feather, a downy undercoat and contour feathers that are arranged in orderly points of attachment to lie down in strategic ways over the down and the skin. This system traps small pockets of air all over the bird’s body.
Feathers are made of beta keratin like their beaks and claws. This substance is tougher than the alpha keratins that make up the finger- and toenails, hair, horns, and hooves of mammals. But in order to remain functional for six months to a year, the feathers have to be maintained. Most songbirds have an oil-producing gland at the base of their tail (formally called the uropygial gland).
You can watch a bird stick its beak back there and scratch at it to stimulate oil release. The bird then preens its feathers with an oil-covered bill to put them in order and to coat them. All birds carry parasites that attack their feathers, and in some bird species symbiotic bacteria around the gland and spread with the oil also serve to protect the birds against these lice and mites.
Individual birds keep warm by remaining active through the day. But what about at night, when it gets even colder and birds have to sleep and hide from night predators? Now you can start making all the jokes about “shared bodily warmth,” except this is exactly what birds do. During the winter hardly any species maintain territories and many flock together for safety in numbers while they forage. When night falls, they will seek out the lee side of a coniferous tree, or somewhere else that offers protection from the wind, and they will huddle together in various configurations. Birds that nest in cavities will return to some sort of hole and congregate there. Brown creepers are known to hunker down in a circle with their heads at the center, but most simply pack themselves side by side.
I bought a tube feeder with an irritating design feature I didn’t notice until it failed. The perches screw in individually rather than being rods that pass entirely through the tube. Two of them fell out while it was stored. The original perches were metal rods coated with plastic. Rather than order replacement perches, I took the feeder to the hardware store and found two machine screws that were the right gauge and length.
But it was important to wrap them with electrical tape before I put it outside. Birds have a remarkable countercurrent heat exchange system in the blood vessels of their legs and feet in order to keep them warm. The downside of warm feet is that they will freeze to the surface of cold exposed metal. No part of your bird feeders should be made of smooth steel or other metal.
The cafeterias and restaurants at ski lodges do a booming business because skiing is a sport that keeps you out in the cold for hours and hours, so you burn a lot of calories just staying warm, never mind what you burn skiing (or snowboarding). Birds are always outside and eat almost continuously even when it isn’t cold, so during the winter they are on the look-out for high-calorie meals to keep their bodies at a constant temperature. Normal body temperature in a bird is often 100 degrees Fahrenheit or more.
Seeds are the calories-storing vessels of plants. In the middle of a seed is the embryo that is the start of the next generation. The embryo is surrounded by the endosperm, which is rich in oils, starches and proteins. These will be used to power the germination of the plant before it reaches the light and starts to generate its own food via photosynthesis.
Of course, many seeds never germinate. If they grew on wild plants, they can fail if they fall in some unfortunate place, but often enough they are harvested by a bird or some other animal that needs those oils, starches and proteins to generate some calories and stay warm.
If the seeds are grown in a cultivated field, then hardly any of them will produce new plants. Fields of sunflowers are extraordinarily beautiful. They are as tall as corn but crowned with yellow flowers 6 to 10 inches across. For some reason I have seen them more often when traveling in Germany—I think they are more commonly consumed by humans there—but growing the seed that goes into bird food is a respectable branch of agriculture in the United States too.
Anyone who has raised chickens knows that they happily eat all kinds of kitchen scraps (including chicken!), so putting out beef suet for birds isn’t really as odd as you might think. Suet is, of course, fat removed from cows. The energy density of beef fat is 8.5; fats have almost twice the energy density of carbohydrates and proteins.
In addition to keeping your feeder station flush, it isn’t a bad idea to clean out your bird houses in the fall. That way your local birds will have a nice clean place to huddle on those cold winter nights.
Bill Chaisson, who has been a birdwatcher since age 11, is a former editor of the Eagle Times. He now works for the Town of Wilmot and lives in Sutton.
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