Are Chickens Mammals? 5 Easy Things to Check

Chicken Care Taker Are Chickens Mammals 2
Chickens are NOT mammals. Instead, chickens are considered birds or fowls. A fowl is a bird that is kept for eggs and meat while roosters are also fowls, not mammals.

For years, there have been debates on whether chickens are birds or mammals. For anyone who is new to chickens or mammals, this can be quite confusing. That is because mammals and chickens do share some of the same characteristics.

Yet birds are different from mammals because they have many different characteristics. 

In this article, we’ll take a closer look at the different characteristics of mammals to demonstrate that chickens are not mammals. 

So let’s dive right in!

Differences between Chickens and Mammals 

There are several major differences between chickens and mammals. The following are five characteristics that will show why chickens are not mammals:

1. All Mammals Have Fur and/or Hair – Chickens (Birds) Have Feathers 

Mammals have only fur and/or hair. On the other hand, chickens and other birds have feathers. Of course, you already know that fur and feathers are totally different things. This clearly shows that chickens are different from mammals. 

See Also:  How To Tell If My Chick is a Rooster?

Feathers are important not only for flying but also for providing warmth and protection, – and in some species, for attracting mates. 

Evidence suggests that mammals and birds descended from two totally different animals.  

Birds evolved from a category of meat-eating dinosaurs known as theropods about 150 million years ago. On the other hand, mammals descended from a group of animals known as synapsids around 320 million years ago.  

2. All Mammals Have the Milk-Producing Glands Called Mammary Glands – Chickens Do Not

Another major characteristic of mammals is that they have milk-producing glands called mammary glands.  

Mammary glands are exocrine glands that produce milk to sustain the mammals’ young offspring. Females have mammary glands that produce milk for sustaining their young offspring and hence, spend a good amount of their time raising the offspring.  

Chickens and other birds do not have mammary glands. Therefore, they cannot produce milk for their baby chicks. 

3. All Mammals Do Have Teeth – Chickens Do Not

Another major difference between mammals and chickens is teeth. While all mammals have teeth, birds and chickens do not.  

Yet chickens enjoy eating nuts and other hard foods. They can do this because of their unique digestive system. When they eat food, it travels to a part known as a crop. The food remains there until it is ready for digestion and travels to the gizzard where it is “chewed up” with a combination of food and gravel. 

Instead of having teeth, birds have developed beaks that aid in flight due to their aerodynamic shape. 

See Also:  How Long Are Roosters Fertile For?

However, chickens have the so-called ‘egg tooth’. This is basically a tooth-like extension on their beaks. Since baby chicks develop in an egg, they need an ‘egg tooth’ to break out. These tooth-like extensions break off soon after they have broken out of the egg shell since they have already played their role. 

4. Mammals Generally Give Birth to Their Offspring – Chickens Lay Eggs 

Mammals generally do not lay eggs. The only two mammals that lay eggs are echidna and platypus. 

Some people think that chickens are reptiles because they also lay eggs. However, reptiles tend to be sluggish when it’s cold because they do not maintain their body temperatures. They rely on the environment to regulate their body temperature. 

Some reptiles will hibernate during cold seasons. Chickens do not hibernate. Some mammals also hibernate. Making it even more confusing whether or not chickens are mammals or reptiles is the fact that fishes lay eggs. 

5. Mammals Are Warm-Blooded Vertebrates

The last thing to mention is that all mammals are able to stay warm in cold conditions. On the other hand, reptiles make themselves warm by sunning on rocks. When it’s very cold, reptiles cannot regulate their metabolism to warm up.  

Mammals can maintain their body temperature, even in cold conditions. This is mainly because they have a backbone (which makes them vertebrates). 

Any animal with bones or an internal skeleton is a vertebrate. That means chickens are also vertebrates.  

Chickens are also warm-blooded animals. They keep themselves warm by regulating their metabolism during cold days. 

Why Some People May Consider Chickens to Be Mammals 

Perhaps the argument that chickens are mammals stems from the fact that birds share some characteristics with mammals. 

See Also:  Did You Know That Chickens Have Ears?
chickens in a pen
Chickens definitely share some characteristics with their mammal counterparts

For example, chickens are warm-blooded animals and take care of their baby chicks.  However, for an animal to be classified as a mammal, it must have teeth, give birth to babies, and produce milk. 

Some people also consider chickens to be mammals like sheep, goats, cows, pigs, and horses because they are all kept on farms. 

Also, both chickens and mammals care for their young ones until they are fully grown and can take care of themselves.  

Frequently Asked Questions 

So Chickens Definitely Aren’t Mammals?

As we’ve outlined above, chickens are birds and not mammals. The major differences include:

  • Chickens have feathers instead of hair or fur
  • Chickens lay eggs 
  • Chickens have no mammary glands 

Why Are Chickens Considered Birds? 

Chickens have wings, feathers, and a beak. They also lay eggs and are warm-blooded. Moreover, they have a gizzard, a crop, a cloaca, and a proventriculus. These are the main characteristics of birds. 

Are Chickens Reptiles or Mammals?

Chickens are neither reptiles nor mammals. Birds fall under their own group, and chickens are considered fowls

The phylum Chordata consists of five major classes: birds, reptiles, amphibians, fish, and mammals.    

Are Birds Omnivorous, Carnivorous, or Herbivorous? 

Generally, birds are omnivores. Chickens eat a wide variety of foods, including corn, seeds, grass, worms, and small reptiles. 

What Class Do Chickens Fall Under? 

The scientific name for chicken is Gallus gallus domesticus. The seven levels of classification of a chicken are: 

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Aves
  • Order: Galliformes
  • Family: Phasianidae
  • Genus: Gallus
  • Species: Gallus gallus


A longtime resident of Southern California, Christina recently moved across the globe to Austria, where she bought land specifically to build a small house with room for a backyard chicken coop. Christina spent her childhood summers on a farm, raising and caring for a flock of hens owned by her grandparents, which prompted a lifelong love of chickens, and other farm animals. Christina is passionate about writing, having written hundreds of articles for well-known websites, and uses her English degree in service of her love for animal welfare, most recently taking on a writing position at Chicken Care Taker in 2022.

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