Are Chickens Birds, Mammals, Or Reptiles?

Are chickens mammals, birds, or perhaps reptiles? When you first see a chicken, the answer might seem obvious. They have feathers, have a beak, and lay eggs – they must be a bird! However, unlike most other birds, they’re not great flyers. Also, both reptiles, and birds lay eggs. All of this can make the question of what exactly chickens are quite confusing and a closer look makes the question more valid than it might initially seem.

To determine once and for all whether or not these animals are mammals, birds, or reptiles, let’s take a look at the differences between them so that we can come to a clear answer.

If you’re in a hurry and need a fast answer, here you go: Chickens are birds, more specifically, they are fowls. They are not reptiles or mammals. They are not mammals because they lay eggs, which mammals do not do. They’re also not reptiles because reptiles are cold-blooded, and chickens are not.

Are chickens reptiles?

All reptiles, without exception, are cold-blooded, meaning that their body temperature is determined by how warm or cold their surroundings are. They do not have a stable internal body-temperature, unlike mammals and birds which are warm-blooded.

Warm-blooded animals have a mostly constant internal body temperature that is higher than their surroundings.

Chickens are not cold-blooded. Their internal temperature is not determined by their surroundings. Because of this, they are not reptiles.

Reptile ancestors

However, while chickens are not reptiles, there is pretty strong evidence that they did in fact descend from them. And not from just any reptile, but the biggest reptiles of them all, the dinosaurs.

They did not directly descend from a T-rex or anything, but rather from the much smaller dinosaur, the velociraptor. You’ve probably seen this dinosaur star in the movie Jurassic Park. In the movie, it’s portrayed as having scales, but in reality, it most likely had feathers and looked something like this:

This is what a Velociraptor is most likely to have looked like – looks much more like a chicken than the ones you see in Jurassic Park!

It’s very likely that, since they descended from Velociraptors, many people assume that chickens are reptiles. However, as I’ve evidenced above, this is not the case.

Are chickens mammals?

Mammals do not lay eggs (there are 2 exceptions, the platypus and the echidna). So no, chickens are definitely not mammals. Also, chickens have feathers, and mammals do not have feathers. Instead, they have hair or fur.

Are chickens birds?

The thing people associated most with birds is flying. Chickens are capable of flying, but they’re not very good at it. Nevertheless, just because they’re not good flyers does not mean that they’re not birds. The ostrich, emu, rhea, kiwi, and cassowary are all birds, yet none of them can fly.

Being able to fly is not a prerequisite for being considered a bird. Instead, birds are defined as follows:

“Birds are a group of warm-blooded vertebrates constituting the class Aves, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.”

So, let’s see if chickens check those boxes: Feathers, check. Toothless beaked jaws, check. Laying of hard-shell eggs, check. High metabolic rate, check. Four-chambered heart, check. Strong lightweight skeleton, check.

So, chickens check all the boxes and are indeed birds!



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