How Do Birds Keep Their
Feet Warm?

By Richard Worden

Humans have a lot of options to stay warm when the mercury dips. We can layer up and cover those extremities most prone to frostbite using gloves, boots, and caps, allowing us to go about our lives unaffected by the weather. But how on earth do birds cope? And how do birds keep their feet warm?

Birds keep their feet warm by transferring heat from their bodies to their feet. They also stand on one foot, cover their feet with plumage by sitting on them, huddle together in groups, shiver, and fluff their feathers to stay warm. Of course, there are limits to what they can tolerate.  

Let me tell you a little more about the wonder of evolution that is the bird's foot. Along the way, I’ll also cover strategies birds use to stay warm.

Birds’ Feet Are Uniquely Well-Adapted to Cold Conditions

When you look at birds shivering in the cold, it’s easy to feel sorry for them. Shriveled and damp, with nary a scarf or mitten in sight, they can look quite fragile indeed. And nothing shrieks vulnerability more than those scrawny exposed feet. Imagine walking around on those things!

But birds' feet aren’t really as ineffectual as they first appear. Having evolved over a 150 million-year period, they’re actually pretty ingenious in design and are uniquely well-suited to a wide range of diverse environments.   

Here’s a brief overview of some of the fantastic features that allow birds to tolerate prolonged exposure to extremely low temperatures.

The Anatomy of Bird Feet

Birds have bony, scaly feet with little muscle, few nerves or pain receptors, and no sweat glands or skin. Each of these features makes birds better suited to living with lower temperatures.

The low or non-presence of muscle, skin, nerves, and pain receptors limits the circulation of blood (which would cool faster) through a bird’s foot, reducing its sensitivity to cold. 

The absence of sweat glands keeps a bird’s foot dry and prevents it from sticking to other frozen surfaces, such as damp overhead wires or a fence or railing. And the minimal amounts of fluids in a bird’s foot significantly reduces the risk of frostbite. 

So, while they may make birds appear vulnerable, birds’ feet are actually very well suited to frigid environments. But, while the features described above help a bird cope with extreme cold by themselves, they wouldn’t be sufficient to enable survival in sub-zero temperatures. 

However, there’s another feature of the bird’s foot that works together with the rest of its specialized biology to give it just the advantage it needs.   

A Unique Way of Exchanging Heat With the Body

As important as all the stuff not present in a bird’s foot is, what is present in it makes all the difference between life and death under the harshest conditions. That’s because the bird’s foot is covered in a miraculous web of veins and arteries that pumps blood between its heart and feet–it’s called the rete mirabile, Latin for  "wonderful net."  

The rete mirabile works like a hydronic radiant heating system that pumps hot water through a house to keep it warm. By constantly pumping warm blood from a bird’s heart through its feet, this circulatory system ensures that the bird’s foot doesn’t freeze.

Strategies Birds Use To Stay Warm

Of course, however well adapted they may be, birds need not particularly enjoy cold weather. So birds also use a lot of other everyday behaviors to make cold tolerable.  

While they haven’t quite cracked fire yet and are not as wily as us humans when it comes to stealing the coats of other animals’ backs, birds do have a few tricks up their sleeves.

Standing on One Foot

You know the pose I’m talking about, that yogic contortion that makes a fowl one-legged, appearing at the same time both lonely and wise and bemused and comical. 

What the gnomic feathered ones are actually up to is tucking their invisible appendages into the luxuriant down of their plumage, where it's much cozier than out in the cold. There’s a reason we steal those things for our coats! 

Tucking Feet Into Plumage

For those birds that would rather squat than stretch, there’s always the option of sitting on their feet. After all, what works with one foot works twice as well with two! Not only are the feathers of a bird warm and waterproof, but they also grow on the body, which tends to be warmer than a bird’s feet.

Huddling Together in Groups

Another favored bird strategy is to huddle together in groups. This works just like it does for humans and many other wild animal species by transferring body heat from one individual to the next. Depending on their habitat, birds will gather together in nests and cavities, on cliffs, in trees and bushes, and even on urban architectural features like wires. 

Shivering and Fluffing Feathers

The rapid repetitive contracting and expanding of muscles, also known as shivering, raise body heat in birds, just as in many other animals. Fluffing works by trapping pockets of warm air among the feathers. Birds often like to fluff their feathers together in groups where it is warmer.

Birds Are Not Invincible

None of what’s been said above should give you the impression that birds’ feet are impervious to extreme cold. Birds can feel severe discomfort. Although their bodies remain warm–around 100°F (38°C) - temperatures in their feet drop significantly below this. They can be close to freezing in the harshest weather.

Moreover, birds have been known to freeze to death on rare occasions. They can be caught unawares by flash freezes in open space or on water. And no bird would survive were it to get trapped in certain conditions, such as deep underwater in a lake that has frozen over.

How Do Birds Keep Their Feet Warm...Conclusion

Birds' feet have particular adaptations that make them more tolerant of extremely low temperatures. They contain low to no muscle, nerves, skin, pain receptors, and sweat glands, and a unique circulatory system that transfers heat from the body of a bird to its feet.

Birds also use a range of everyday behaviors to stay more comfortable in the cold. These include hiding their feet in their feathers, flocking together, shivering, and fluffing feathers.

None of this makes them completely impervious to cold, and, in the worst cases, birds have frozen to death.

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Hi! I'm Richard Worden, the author and founder of We Know Birds.

Over 20 years ago I developed a keen interest in birds and birdwatching, and it has been my passion ever since. I am committed to spreading useful knowledge about birds to others so we might all enjoy them to the fullest.

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