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Are Birds Cold-Blooded? What You Need to Know!

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gray catbird perched on a branch

Like humans and other mammals, birds are warm-blooded, not cold-blooded. This means that their body relies on several mechanisms in order to remain at a relatively consistent temperature, which is around 106 degrees Fahrenheit for most birds.

This fact is surprising to many since birds can withstand harsh environments and freezing temperatures on a regular basis. Even so, birds have evolved so that their body remains at the needed temperature for survival. In other words, birds are not cold-blooded.

Keep reading to learn why birds are not cold-blooded and how they survive in incredibly cold environments.

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What Is The Difference Between Cold-Blooded And Warm-Blooded?

In order to understand why birds are not cold-blooded, it’s imperative to understand the difference between cold-blooded and warm-blooded animals. In short, warm-blooded animals can regulate their own body temperatures, whereas cold-blooded animals cannot.

Let’s take a closer look at each classification.

sparrow singing

Image Credit: GAIMARD, Pixabay


Cold-blooded animals cannot regulate their own body temperature—these animals rely on the environment around them to establish their internal temperature. Consequently, the temperature of cold-blooded animals changes with their location, the season, and the time of day.

Since cold-blooded animals rely on their environment for temperature regulation, they are incredibly sensitive to their environment. Due to this fact, individual cold-blooded species are often found in only a few places around the globe.

Reptiles, amphibians, fish, insects, and invertebrates are most often cold-blooded. It is for this reason that pet snakes and lizards must have a heater inside their cage. The heater is required in order for the reptile to stay warm.


Warm-blooded animals, in comparison, can maintain their own internal temperature. They do not rely on the environment around them to maintain the temperature. Their body has developed mechanisms—mostly metabolic regulation—to maintain the internal temperature even in extreme scenarios.

All mammals and birds are warm-blooded. This means that you, your dog, your guinea pig, and the robin outside are all warm-blooded. The mechanisms the animal uses to maintain its internal temperature vary from species to species, as does the exact internal temperature.

For example, humans sweat whenever they are hot in order to bring the internal temperature down. Dogs, in contrast, pant. Although the mechanism differs from species to species, the end goal is all the same—internal temperature regulation.

Lucifer Hummingbird

Image Credit: Rob Palmer Photography, Shutterstock

Related Read: Do Birds Sweat? How Do They Regulate Heat?

Why Are Birds Warm-Blooded?

That brings us to birds specifically. Why are birds warm-blooded? The specific reason why warm-blooded animals exist is unclear, and the same is true of birds. Some scientists speculate that warm-bloodedness developed as a way to fight fungal infections, but it is unclear.

However, scientists do know that birds evolved from a group of dinosaurs called theropods. The T-Rex is the most well-known theropod. Although it may be strange to think of a T-Rex as the ancestor of a bird, just think about the T-Rex’s body—it basically looks like a giant chicken without feathers!

What’s important to understand about theropods is that most scientists believe these creatures were warm-blooded. Because birds evolved from theropods, they are warm-blooded as well.

Because birds are warm-blooded, they have been able to survive on all continents and in many conditions. Some birds are better suited for colder environments, whereas others are better suited for hot environments. Either way, all birds are warm-blooded due to their dinosaur ancestors.eagle divider

How Do Birds Not Freeze In The Winter?

As we learned above, warm-blooded creatures can maintain their internal temperature through various natural mechanisms. What are these mechanisms in birds? How do birds not freeze in the winter?

There are several bodily mechanisms at play to keep birds at a healthy internal temperature. Often, multiple mechanisms are at play at the same time to ensure the bird stays warm. Let’s take a look at the most common three.

1. Plumage

Plumage is one of the most obvious ways that birds regulate their internal temperatures during the winter. Whenever it gets cold, some birds add additional feathers and fat in order to insulate themselves from the cold.

The additional fat also provides birds with an additional energy source. During the winter, additional fat will be burned in order to increase the internal temperature. So, this extra layer of fat helps to ensure birds do not freeze in the winter. Finches are one of the most common birds that use this technique.

Additional plumage isn’t always an option for birds, unfortunately. Small birds are sensitive to how much weight is on their body. If they are too heavy, they won’t be able to fly. Hence, many small birds cannot add additional feathers and fat to their bodies in the winter because they won’t be able to survive.

Kakapo Parrot during winter

Image Credit: heather_p, Shutterstock

2. Heat Exchange

Heat exchange within the body also keeps the internal temperature constant from the inside out. How it works is that warm, oxygenated blood moves towards the bird’s extremities. The veins that bring the blood in are very close in proximity to the veins that bring the blood back to the heart. Because the veins are so close, heat is naturally exchanged between them, keeping the extremities warm.

Heat exchange is especially important for keeping the bird’s feet warm during the winter. As you probably know, many birds do not have feathers on their legs and feet. The heat exchange helps to prevent any freezing. Geese, ducks, and waterfowl especially depend on heat exchange since they spend some of their time in cold water.

Birds are not the only warm-blooded animals that rely on heat exchange. In fact, nearly all warm-blooded animals rely on heat exchange to some degree—including you!

3. Physical Reactions

Birds will sometimes even physically respond to the temperature in order to stay warm. There are a lot of migratory birds that will fly south during the winter. This is done in order to prevent freezing and have access to more food sources.

Some physical reactions to cold are much more subtle. Just like us, some birds will actually shiver whenever they are cold. Chickadees are one such species that does this. Shivering birds don’t quite look like shivering humans, though. Whenever birds shiver, they activate muscle groups so that they work in opposition to one another, creating warmth.

tufted titmouse during winter

Image Credit: MikeGoad, Pixabay

eagle dividerFinal Thoughts

In conclusion, birds are warm-blooded, which means they regulate their own internal temperatures through various mechanisms. Mechanisms like additional plumage, heat exchange, and physical reactions keep the bird warm, even in the winter.

Since birds are warm-blooded, you don’t need to panic when you see those adorable feathery friends outside your window during the winter. Their bodies have evolved in such a way that they can survive in the winter.

Featured Image Credit: JackBulmer, Pixabay

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.

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