This week’s question was asked by a friend.
QUESTION: How do birds avoid frostbite in winter?
ANSWER: There are different coping strategies for different species of birds. Birds can’t eat themselves silly, like a bear, and put on a lot of weight. They would never get off the ground or limb.
Migration is a great plan. Get out of the cold north and go south. It’s not for every bird. Migration takes a lot of energy, and migration takes its toll. Much time is spent flying instead of eating. There’s lots of predators on the flyways. Navigation is iffy. Most birds that die during migration do so on their first flight. The majority of those die by running into bad weather.
What about the birds that stay in our frozen north? The down feathers of birds provide an excellent insulating layer of fine feathers under the exterior tough feathers. Down is used in jackets, bedding, sleeping bags and pillows. Some birds grow extra down during cold weather. Birds preen, or “fluff up,” their feathers, trapping air between the feathery layers.
Birds have oil-producing glands that allow them to waterproof the outer feathers. It keeps the down dry. Air in the down feathers is a good insulator but water is deadly. Water transmits heat.
What about the feet of birds? Many sit in a position that covers a good part of their legs and feet that are somewhat protected by their down. They crouch down and cover both feet with their plumage. Some hunker down in areas protected from the wind. Others, such as chickadees, will roost together in clumps giving each other protection.
The legs of most birds have an incredibly small surface area compared to the rest of the body. This limits the amount of skin exposed to the cold. Bird feet are covered by scales, mostly bone and sinew. There is very little tissue that cold can damage. Some birds have an adaptation to their circulatory system whereby blood is circulated between colder outer areas and warmer inner areas.
We humans shiver when we are cold and so do birds. Shivering is small muscle movement that creates warmth by expending energy. Birds also shiver.
Birds will find a place in the sun and soak up some solar energy. Birds may eat slightly more and have been observed to pick out foods which have high energy value. They also seem to be able to remember where that source is located, which cuts down on foraging time.
Birds avoid things in the winter that take a lot of energy. Singing is one of those activities. We have those beautiful bright-red cardinals year around in Monroe County. They seldom sing in the winter. You know spring is here when you hear the beautiful song of the cardinal.
It’s obvious that birds don’t build nests, lay eggs and tend to the young in the winter. They don’t defend their territory. All that activity is too much work, so they lay low and hunker down.
What about those big webbed geese and duck feet? Nature has a special adaptation for them. Their veins and arteries are aligned in such a way as to enable heat exchange between warm blood being pumped toward the feet and cool blood being pumped away from the feet. Cool blood from the feet is warmed before it reaches the bird’s core. The core blood is cooled before it reaches the feet. The lucky duck or goose can have a body core temperature of around 104 degrees Fahrenheit while their feet can be in water that is near freezing. It’s another miracle of nature.
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