How birds survive winter’s bitter cold

Some clues: they begin building up fat reserves as insulation in the fall; they grow about 1,000 new feathers; they puff themselves up, using many calories, to produce extra body heat.

Sherrie Versluis Feathered Friends
Sherrie Versluis
Feathered Friends

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 as we are adorned in thick, down-filled coats with toques and mitts, it is still bitter and unbearable. When the wind chill kicks in, it 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 compared, to about 98 degrees for humans. Keeping up these temperatures requires a lot of calories in winter. Preparations for the cold season begin in fall when wild birds begin to build up fat reserves. At that time of year food sources are plentiful; many plants have gone to seed and birds will eat excessive amounts. An extra layer of fat serves as insulation and can provide the extra energy needed to maintain their body temperature.

Oiled feathers for insulation

Feathers are obviously the staple in enabling them to stay warm. In fact, wild birds will grow about 1,000 new feathers for winter, mostly down feathers which lie 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 is actually a way to produce more body heat. The method is only used in the coldest of weather as it uses up 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 along its body, from the tail upwards. This action spreads the oil throughout its feathers. Properly preened feathers are imperative for wild birds, especially in winter.

I have been asked many times why birds’ skinny little legs don’t freeze off. The reason: 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 is how wild birds make it through the long, severely cold winter nights. Some birds like chickadees and nuthatches will roost together in small groups inside a cavity where they will share their body heat. This may be a natural tree cavity or a human-provided source like a birdhouse or winter roost. I once saw a picture of about 16 chickadees packed inside a roost, like a little puzzle.

Another skill birds use during the night is to go into a state of torpor. In this state of reduced metabolism, they reduce their body heat by about 50 degrees. This is a major way to reduce and conserve calories but it can be dangerous. In this state birds are vulnerable to attacks by predators, as their reaction times will be very slow until they bring their metabolism back up.

To help give wild birds a bit of an edge on winter here are some tips. Provide black oil sunflower as a staple food; this seed is very high in fat and eaten by all birds in winter. You can also consider shelled sunflower which makes the food even more accessible to them.

A quality suet is an excellent source of fat, energy and calories and is a great attraction for woodpeckers and nuthatches in particular.

Keep water within reach

The availability of water is a big deal for birds in respect to preening. Water is used to wet the oil gland, making it easier to disperse the oil throughout their body. It also assists them in digesting foods in the cold. Heated birdbaths are a great way to offer water; don’t worry, birds will not bathe in the same way they do in summer.

Birdhouses left outside will provide shelters for birds to roost in during the night.

Wild birds are not dependent on feeding stations as they are always able to find natural foods, but you can make their lives much easier by offering high quality foods and keeping your feeders full. In return, you will be treated to the antics and beauty of wild birds all season long. This will keep your spirits as bright and cheerful as are the birds themselves.

Sherrie Versluis owns The Preferred Perch on St. Mary’s Road in St. Vital, phone 204-257-3724.

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