How is it that winter’s brutal cold doesn’t appear to faze them? Birds have the highest body temperature in the animal world.
By Sherrie Versluis
How do they do it? How do wild birds survive in the dead cold of winter? We all know as humans that when the thermometer hits minus 20 or colder we hurry from the car to the house. Even when we are decked out in thick, down-filled coats with toques and mitts, it is still bitter and unbearable. When the wind chill kicks in those temperatures can even be life threatening. Yet, wild birds carry on each day seemingly unbothered by the brutality of winter. What do they have that we don’t?
Birds have the highest body temperature in the animal world, ranging from 105 to 112 degrees Fahrenheit compared to about 98 degrees for humans. It requires a lot of calories to maintain these temperatures in winter. Preparations for the cold season begin in the fall when wild birds start to build up fat reserves. At that time of year, food sources are plentiful, as many plants have gone to seed, and birds will eat excessive amounts. This extra layer of fat serves as insulation and can provide the extra energy needed to maintain their body temperature.
Down for the winter
Feathers are obviously the staple in equipping birds to stay warm. In fact, wild birds will grow about a thousand new feathers for winter! These are mostly down feathers which are closer to the skin.
You may witness birds shivering and puffed out in winter but, they are not doing this because they are cold. It’s one way for them to produce more body heat. The technique is only used in the coldest of weather as it requires a lot of energy and calories. The exterior feathers provide a source of water and wind-proofing as well as insulation.
All birds have an oil gland located at the base of their tails. You may sometimes see a bird rubbing its head from the tail upwards. This preening is how birds spread that oil throughout their feathers. Properly preened feathers are imperative for wild birds especially in winter.
I have been asked many times how birds’ skinny little legs don’t freeze off. Their legs are designed with very hard scales that reduce heat loss. Birds can also control the temperature of their legs separately from the rest of their body by restricting blood flow. Sometimes birds will tuck their head under their wing and crouch down to keep their faces and legs warm. On sunny winter days, birds take full advantage of the sun’s warm touch. They will find a perch in direct sunlight and warm their bodies to conserve calories.
The most surprising thing about wild birds in winter is how they make it through the long, severely cold nights. Some birds, like chickadees and nuthatches, will roost together in small groups inside a cavity. They may find a natural tree cavity or a human-provided source like a birdhouse or winter roost where they will share their body heat. I once saw a picture of about 16 chickadees packed inside a roost like a little puzzle.
Another skill birds use is to go into a state of torpor during the night. Torpor is a state of lowered metabolism where they reduce their body heat by about 50 degrees. It is for them an important way to reduce and conserve calories, but this can be dangerous. Their reaction time while in this state is very slow, making them vulnerable to attack by predators.
Here are some tips on helping wild birds obtain a bit of an edge on winter. Provide black oil sunflower as a staple food. This seed is very high in fat and appeals to all birds in winter. You can also consider shelled sunflower, which makes things even easier for them. A quality suet is an excellent source of fat, energy and calories, and a great favourite of woodpeckers and nuthatches in particular.
Put out quality food
Finding water is extremely important for birds when they’re ready for preening. Water is used to wet the oil gland, making it easier to disperse the oil throughout their body. It also assists in digestion in the cold. Heated birdbaths are a fabulous way to offer birds water. Don’t worry, though. You won’t see the birds bathing the way they do in summer. Another offering they appreciate is a birdhouse. A birdhouse left outdoors will provide shelter for birds to roost in during the night.
Wild birds are always able to find natural foods, and so they aren’t dependent on feeding stations. But life becomes much easier for them if you keep your feeders filled with offerings of high-quality foods.
In return, you will be treated to the beauty and antics of wild birds all season long. This will keep your spirits as bright and cheerful as the birds themselves.
Sherrie Versluis owns The Preferred Perch, at 204-257-3724.
(The first edition was published on Feb 2, 2022)
@ 2023 Pegasus Publications Canada’s Local Gardener Lifestyles 55
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