Wildlife: Metabolism, feathers help birds survive winter nights
Share with others: The long, cold winter nights that lie ahead
make day-to-day survival a challenge for wild birds. Smaller
birds face the greatest problem because they lose heat more
rapidly than larger birds. Wherever a bird sleeps, its first
line of defense against cold is its feathers. Feathers repel
water and efficiently insulate warm bodies from cold winter air.
Each feather is controlled by a group of small muscles that can
raise and lower the feather. By fluffing their feathers, birds
create many tiny air spaces that increase insulation and reduce
heat loss. On extremely cold nights, birds reduce heat loss
further by burying naked body parts into their feathers. This is
why birds tuck their bills into their shoulder feathers and why
many water birds often sleep with one leg held tightly up
against the body. During the day, birds feed constantly to fuel
the metabolic furnace that keeps them warm through the night.
Backyard feeders are busi