Are birds warm-blooded? How do birds survive during Winter?

Everything is frozen outside, there is a huge cold snap happening, but still, you see birds flying around as if somehow, they’re immune to cold. Are birds warm-blooded after all? Let’s check on this article.

Surprisingly, they are warm-blooded and their body temperatures are actually slightly warmer than ours. To keep this temperature, birds have to be smart about how they shelter themselves from the cold during Winter.

What does it mean to be warm-blooded?

Warm-blooded animals, which are mostly birds and mammals, need to maintain a relatively constant body temperature or they would suffer dire consequences. It doesn’t matter what the outside temperature is—they must keep the same internal temperature, no matter what happens.

Because birds are warm-blooded, it means they can maintain a constant body temperature and do not need to rely on an external heat source to stay warm. That means that can live anywhere on the globe, as long as they can keep the same temperature. Around 106 degrees Fahrenheit or 41 celsius to be exact.

Additionally, birds, especially passerine birds, have high basal metabolic rates. That gives them a higher body temperature when compared to mammals and it means they use a lot of energy.

How do birds survive during Winter?

Surviving during Winter has less to do with temperature than with food availability. Given that there is a reliable food supply available, birds can usually cope with the cold with no problems. Below are some tricks their use to survive during Winter.

Being ’round’ and puffing feathers helps

According to an article by ACS, “small warm-blooded animals tend to have a rounded shape, which ensures that the interior of an organism stays warm the longest time possible. “

This is because the heat they lose is proportional to the surface area of their bodies, while the heat they produce is proportional to their mass.

This means that larger animals can generate more heat than they lose and they can keep their body temperatures stable more easily. That is also the reason why birds tend to be larger in the temperate zones than in the tropics.

However, one of the main reasons that help birds keep their warmth during cold days is due to how their feathers work. During Winter, birds have extra plumage that acts like a coat, insulating their bodies.

round bird
Photo by Wallmika

As seen in our article Why Do Birds Fluff Up Their Feathers? feathers provide insulation and are coated with an oil that promotes waterproofing.

When it gets colder, birds puff out their feathers to increase the amount of air next to the body. 

By puffing up his feathers so they almost stand on end he traps warm air next to his internal organs. Air is an excellent insulator meaning even a few millimeters under the feathers will keep birds nice and warm.

Birds fluff up their feathers in the cold so they trap as much air as possible in tiny pockets of air to hold in body heat.

Huddling together

When it’s cold outside, it might be a good idea to huddle with your buddies. That is what many birds do to survive during nighttime and cold snaps.

huddling penguins
 (Image credit: Daniel P. Zitterbart, AWI)

Sparrows, for example, seek out shelter in dense foliage or cavities to avoid the elements. 

In another example, the emperor Penguins huddle together to save energy and keep themselves warm during the breeding season in Antarctica. Previous research has suggested that individual penguins within a huddle regularly make small movements roughly every 30 to 60 seconds, traveling between 2 and 4 inches (5 and 10 centimeters) with each step to keep incubated eggs warm.

Tucking their beaks

When birds get cold, we often see them hide their beak in their feathers to stay warm. That probably happens because their beaks act like a radiator that helps them to cool down when it’s too hot.

Furthermore, biologists have demonstrated that on average, birds that live in cold climates have smaller bills.

Hiding in a mini ‘oasis

Hiding in burrows might be a good solution when is -50ºC (-58 Fahrenheit) outside. That includes snow. Fluffy snow can contain up to 90% trapped air.

The Willow Ptarmigan spends up to 80% of the time in the winter in snow burrows. If snow is deep and temperatures low, dig snow burrow at dusk for overnight use and dig into the snow until beneath surface.

Other wild birds also roost together or find tree cavities to keep heat.


Birds can generate heat by shivering. When birds shiver, they are able to activate particular muscle groups that work in opposition to one another. This causes muscle contractions that allow the birds to better retain their body heat.

But this is a temporary fix that requires a fast metabolism and increased food intake. Chickadees are known for using this strategy since they can’t stack much fat in their little bodies.

Stacking up

Either stacking up on extra plumages, fat, or food supplies, birds find their way around adversities to survive during Winter.

Chickadee about to store this delicious peanut in a tree crevice for a snack later
This Chickadee is about to store this delicious peanut in a tree crevice for a snack later

Chickadees, as mentioned above, can’t storage much fat in their bodies.  They can’t bulk up too much because it would affect how they fly.

To compensate for that, besides shivering, they also stash food in tree crevices.

How birds keep legs and feet warm?

If feathers protect their bodies from cold, how about their legs and feet? How do birds keep their legs and feet warm?

Through a complex process called ‘Countercurrent heat exchange’. To explain in the most simpler way, imagine that the blood in their legs is flowing like two adjacent tubes.

In one tube, the flow comes in warmer because it’s coming from the body. The other tube comes back from the feet with blood that has a slightly colder temperature. But because this tube it’s so close to the incoming warm blood vein, it gets warmer. So, even a duck standing on ice loses little heat from its feet.

No need for moisturizer

Additionally, besides the countercurrent heat exchange trick, birds have another trick in their feet. Remember how we get dry and scaly skin that is damaged by the cold?

As it turns out, the dry, dinosaur-like scaly skin that covers birds’ legs and feet prevents the skin drying and the tissue damage that we would experience in cold situations.

Do birds feel cold?

The ones that can’t adjust to cold climates do, and they solve this problem by migrating to warmer areas.

You can tell a bird is cold if you see it shivering or puffing up its feathers.

How do birds stay warm at night?

Most of the time, birds stay warm at night by puffing up their feathers and sharing body heat with their peers. They will also eat high-energy food to warm and their bodies will burn stored fat to add some extra needed heat on cold nights.

hummingbird sleeping
Hummingbird in torpor state

Birds can also get into a torpor state. Torpor is a sleep state similar to hibernation, a strategy that helps the birds survive during cold temperatures. It is employed by birds like hummingbirds and doves to get through the colder months.

How to help birds during the cold weather?

During Winter, food is like a furnace that keeps birds going. It’s really important that they eat as much as possible since death is imminent if they burn much of their precious fat reserve.

This intense need for incoming food and the risks associated with not getting any soon enough is the reason why many songbirds migrate. For the ones that choose to stay, such as Anna’s hummingbird, for instance, we can give them a little push.

Install a hummingbird feeder

Here on the West Coast of North America (from where I write this blog!), there are one species of hummingbird that never migrate. It’s the brave Anna’s hummingbird! It could have an easier life in Winter if we give him a little push by installing a hummingbird feeder.

It’s very easy to find a hummingbird feeder in any department store. Once you find it, you can install a visible tall pole on your balcony.

You need to fill the feeder with a mixture of 1 part sugar to 4 parts water. It’s important to keep it clean and change the water every 7 days.

Don’t let it freeze! If the feeder is frozen and the bird tries to feed, it might get its tongue stuck there. If you can’t have a heated hummingbird feeder, put it inside if it gets frozen.

Offer peanuts!

If you’re going for a brisk walk around an icy lake, like we did this weekend, it doesn’t hurt to bring a few peanuts with you. There is a chance you will make friends with chickadees, towhees, juncos, and other passerine birds.

Peanuts are an extremely valuable source of fat for birds during Winter, basically a precious fuel to keep going doing cold snaps.

Chickadee feeding off my husband's hands
Chickadee feeding off my husband’s hands


Being warm-blooded creatures, birds need to stock up in body fat and extra feathers to survive during Winter. Keeping themselves warm is a top priority and they do it by using many different strategies: from huddling with friends to eating lots of food.