What Makes A Penguin A Bird? Is A Penguin A Bird? Really!

Penguins are aquatic flightless birds that belong to the Spheniscidae family.

These birds are unique in more than one way but they also share similarities with different classes of animals which is why there is a lot of ambiguity regarding the classification of penguins.

People often categorize penguins into different classes. Being excellent swimmers, penguins are often assumed as fishes.

Another assumption that goes around them is that they are mammals because of their large size and great parenting.

All these different conceptions often raise a common question about what makes a penguin a bird.

To help you get all the required information about why these creatures are zoologically classified as birds below is a detailed article about the same.

Why are penguins considered birds?

Despite having few differences, penguins are considered birds due to various similarities they share with the members of class ‘Aves’ of the animal kingdom.

These creatures fulfill all the basic biological requirements that must be classified as birds.

Below is a list of all the key differences and similarities between penguins and other birds to explain why penguins are considered birds.

Penguins vs Other birds:


1. Penguins lack the ability to fly

The wings of penguins have evolved for swimming as they are used as solid flippers in the water.

Their wings are not suitable for flying because they lack flight feathers. Also, their wings cannot be folded like other birds.

2. Penguins do not have hollow bones

These creatures have solid bones, unlike other birds that have hollow bones which make them lightweight and suitable for flying in the air.

The solid bones help them propel deeper into the water by providing them required mass and weight.

Their bones also help them to manage water pressure when swimming.

3. Penguins are excellent at swimming

Due to the various adaptations that penguins have made over the years, they can swim extremely well. They use their feet and flippers to propel their tails to change directions.

The speed at which penguins swim underwater varies from 15 to 25 miles per hour.

4. Penguins inhabit harsh Antarctic regions

Unlike most other birds, penguins live in some places where the weather conditions are extremely harsh. Over years, they have learned to survive in such conditions with the help of various adaptations.

Related Read: What Are The Longest Lived Birds ( Lifespan Of Birds List, Types, Care )


1. Penguins have feathers

Feathers are one of the basic biological requirements of being a bird. So, like other birds, penguins have feathers. However, they are short and stiff.

The feathers provide insulation from cold to these birds as they trap the air underneath them, they are able to do so because they are closely overlapped to form a thick layer.

2. Penguins lay eggs

Like all birds, penguins lay eggs. They usually lay one or two eggs per season. Their eggs are hard-shelled.  

3. Penguins are warm-blooded

Irrespective of the exterior temperature, birds maintain a persistent body temperature. Being warm-blooded, penguins share this quality with other birds.

Even after living in regions where the temperature drops below -40-degree Celsius, penguins can maintain a constant temperature and keep themselves warm.

4. Penguins have beaks

Like all other birds, penguins have toothless jaws and powerful bills as well. They catch their prey with the help of their bills or beaks. In addition, they have a spiny tongue which helps them to have a grip on slippery food.   

Related Read: Birds Body Parts: 21 Things And Facts You Should Know

In reality, Is a penguin mammal or a bird?

Despite having few similarities with mammals like their upright stance, high agility in the water, method of huddling together in groups to conserve heat, and their feathers giving an impression of fur, a penguin is not a mammal but a bird.

Below are some of the reasons why penguins are not mammals but birds.

  • One of the most important characteristics of mammals is that they give birth to young ones. Also, female mammals have mammary glands to feed their young ones. To fall in the category of mammals, it is required for penguins have these characteristics. But the reality is they lay eggs and do not have any mammary glands. The bird feeds its young with regurgitated food like squid, fish, and krill, like other birds.
  • Penguins do not have hairs or fur on their body like all other mammals. Their feathers may appear like fur as they are short and stiff but in reality, they are not. The appearance and oily texture of feathers is to help the bird bear cold.
  • Most mammals have teeth but penguins are toothless. They have bills like birds which they use to catch prey and feed on them.

Related Read: Can You Feed Birds Bread? | Will Birds Eat Bread?

Why is a penguin a bird and not a fish?

Penguins are seabirds that spend half of their lives in water. Just because these birds are excellent swimmers and island-dwellers, they cannot be categorized as fishes.

They are not cold-blooded like fishes but rather are warm-blooded. Also, the bird has a four-chambered heart, unlike the fish which has a two-chambered one.

Another major difference between penguins and fishes is that penguins have wings that work as flippers whereas fishes have fins for swimming.

What type of bird is a penguin?

A penguin is classified as a flightless seabird. These creatures are called so because they fall into the groups of Aequornithes and Austrodyptornithes which describe them as seabirds. Also, they lack the ability to fly.

Why are penguins classified as birds when they don’t fly?

Penguins are classified as birds despite being unable to fly because flying is not a parameter for an animal to be considered a bird. In fact, there is a completely different category for flightless birds.

So, not only penguins but many other creatures are flightless yet fall into the category of birds. As discussed above, penguins fulfill all the essential biological parameters to be considered as birds.  

What other birds have wings but cannot fly?

Other then penguins, various other birds have wings but cannot fly. Some of those birds are:

  • Australian emu
  • Ostrich
  • Cassowaries
  • Kiwis
  • Rheas
  • Kakapo
  • Auckland Island Teals
  • Steamer Ducks
  • Tasmanian Hen
  • Takahe
  • Roadrunner Bird

What other birds are closely similar to penguins?

The birds that are closely similar to penguins, especially based on appearance, generally belong to the Alcidae family of birds. Some of them are:

1. Common Murre

Similar to penguins, the common murre is a bird that also spends its time mostly in waters in the regions of the North Pacific and North Atlantic.

It also has black plumage at the back and a white one on the belly. The bird is great at swimming too.

2. Little Auk

Little auk is a bird that not only looks similar to a penguin but also hunts like it by diving underwater. Similar to penguins, the birds breed in large colonies.

3. Razorbill

Another member of the auk family, the Razorbill thrives in sub-arctic waters and feeds on crustaceans and fish-like penguins. Other than having a similar appearance to penguins, these birds also nest similar to most species of penguins.

4. Puffin

Puffins top the list of birds that look similar to penguins. They also share many behavioral similarities with penguins such as breeding in large colonies, living in the Atlantic region, nesting, and diving into the water to find prey.

Which species did penguins evolve from?

There are many different conceptions regarding the evolution of penguins but generally, it is believed that these birds have actually evolved from a flying ancestor and then over years, they independently turned flightless.

The fossils of early penguins of over 60 million years ago provided us with evidence regarding penguins being flightless even then. This was the period of about 6 million years after the extinction of flightless dinosaurs.

Thus, it also suggests that penguins have evolved from dinosaurs like all other birds because, in the Jurassic era, birds were one of many different dinosaur species.

What are penguins related to?

Penguins are considered to be related to more than 17 species. If considered morphologically, these birds are considered to be related to albatross, shearwaters, and petrels that are known as Procellariiformes.

Loons, belonging to the group called Gaviiformes, are other species of birds that are considered as closest relatives of penguins. A new clade, Sphenisciformes, is also considered related to penguins based on morphological and behavioral characteristics.

Other groups of the clade to which penguins belong include Ciconiiformes (storks), Pelecaniformes (spoonbills, herons, ibises, pelicans, egrets, hamerkops, and shoebills), and Suliformes (shags, anhinga, cormorants).


Penguins do not fly but it does not mean that they are not birds. They are scientifically classified as birds as they share all the basic traits with them.

They might have few common traits with mammals, reptiles, or fishes, but these creatures are indeed birds.