Is your bird feeder being visited by gigantic Blue Jays and Black-capped Chickadees during this cold spell? Your eyes aren’t fooling you; birds often appear larger in very cold weather.
Birds that remain in New England year round must not only be able to find enough food in the winter to produce heat and energy, they must find a way to retain the heat. Various strategies have evolved, but feather structure and function play an important role for the winter survival of all birds. There are different types of feathers, each designed for a different function. A (wing or tail) feather consists of a central, hollow shaft on either side of which are many interlocking rows of barbs. The feathers that cover the body of a bird (contour feathers) often have interlocking barbs only at the ends, on the part not covered by an overlapping feather. The bottom-most, unconnected barbs on these feathers are similar to those of down feathers – loose and fluffy. When the temperature dips, birds often puff out their contour feathers (making the birds look huge). This action, and the structure of the bottom portion of the contour feathers,
increase the number and size of air pockets between the bird’s feathers and its skin. This space provides excellent insulation, preventing much of the bird’s body heat from escaping.
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This year’s Common Loon chicks are now roughly two months old. Even without being aware of when it hatched, you can estimate the age of a chick by looking at its feathers. Their color and type (down or contour) can give you a good idea of how many weeks old it is. Common Loon chicks are born covered with sooty-black down. By the time they are three weeks old they have replaced this natal down with a second (gray-brown) down. Juvenal feathers start appearing soon thereafter, replacing the down — the age of a chick can be estimated by the amount of down that remains. By eight weeks of age the chicks have just small tufts of brown down remaining on their head and neck (see photo). By nine weeks of age their entire body, including their head and neck, are covered with smooth, gray contour feathers and there is no sign of down.