So how do birds stay warm as temperatures drop below freezing in the winter? The answer is that birds have many ways to combat the effects of frigid winters.
To begin with, birds naturally have a higher metabolism and thus higher body temperature per ounce or pound than humans do. While there is a great deal of variance between species, birds have an average internal temperature of 105 degrees Fahrenheit.
But what are some other ways birds are equipped to deal with cold temperatures?
Prepping in the Fall
One of the first ways a winter bird can survive the winter is to prepare their bodies in the autumn. For some birds, this will mean migrating to warmer regions in the fall. But for birds who stick around, there are a few ways to get ready for cold winters.
Birds who live in cold climates with even colder winters will eat a little extra in the fall. The extra layer of fat not only serves as additional insulation but will come in handy if food is more scarce in the winter.
Extra Warm Feathers
Some species of birds will grow special feathers through their autumn molt to prepare for winter. These feathers are thick and warm and keep a bird nice and toasty in even sub-zero temps.
Some birds can weatherproof their feathers in preparation for harsh weather. They use oil from their uropygial gland to make their feathers better at insulating their bodies. Some birds even can make their wings more water resistant so that they can keep their under-feathers dry. A bird's feathers are its first line of defense against the cold so keeping them clean, dry, and flexible is very important.
Staying Warm in Winter
Once the cold winds have blown in winter, birds still have a lot of ways to stay safe and warm. These methods are so effective that some species maintain body temperatures of 100 degrees Fahrenheit even when the air temperatures are 0 degrees.
Fluffing for Insulation
Have you ever noticed how puffy and fat birds can look in the winter? There is a reason for that. Birds “fluff” their feathers by trapping pockets around their bodies for insulation. These pockets of air keep warm air in and cold air out effectively warming a bird even on bitterly cold days.
You may have also noticed that birds seem more active in the winter. This is more true of some species than others but by remaining active birds can keep their bodies warm. The tradeoff however is that more energy is used, and it makes it more important that these birds find good food throughout the winter.
Shivering as a Short-Term Solution
Just like humans, birds can shiver to bring up their body temperature for short-term warming. The amount of energy required to maintain these temperatures with shivering does not make it a good long-term solution.
Knowing Where the Food Is
A big part of surviving cold winters is the food supply. Birds have to remember where food is so that they continue to have the energy to stay warm through the winter. If you are a bird lover, this is a great time of year to set out high-quality calorie, high-fat foods for wild birds.
Sleeping for Warmth
What about the cold nights? How do birds stay warm when the sun has gone down, and the temperatures drop even further?
Roosting with Other Birds
To stay warm at night some species of birds will roost together to stay warm and share body heat. Birds will line up along tree branches or power lines snuggled up tight against each other to keep warm while they sleep.
Roosting in Natural Cavities or Windbreaks
Cavity nesters stay warm by sleeping in holes in trees and rocks. Birds also make use of natural windbreaks like low bushes and shrubs. This not only protects them from harsh weather but also protects them against predators. Roosting boxes are another way humans can help birds in the winter by providing a protected space where they can sleep safely.
Conserving Energy When Resting
There are a few ways birds are equipped to handle cold temperatures when they are roosting or sleeping. Some birds have feet with unique scales that help reduce heat loss from the body. Waterbirds often sleep on one leg at a time or lay down to conceiver energy and reduce the amount of heat lost from their bodies.
Some birds also have the unique ability to reduce blood flow to and from extremities. This is called countercurrent heat exchange. It isolates the blood flowing to a bird's legs rather than circulating it throughout the entire body. This greatly reduces heat loss while a bird is resting. Birds will also tuck their bills or beaks into their shoulder feathers so they can breathe the warmer air nearer their bodies.
Birds can reduce their metabolic state and internal body temperature. This causes them to enter a state called torpor. Being in a torpor can conserve a lot of energy. Some birds can reduce their internal temperature by as much as 50 degrees. But torpor can be dangerous too. Birds in torpor have a much slower reaction time and are more vulnerable to predators.
In the end, birds have a lot of ways to stay warm in the winter. You can help by providing clean water, quality seeds, nuts, and suet, and maybe even setting up a few roosting boxes.
But even if you don’t, wild birds know how to survive even in the harshest of winter conditions.