Why are Penguins Birds

Watching penguins on TV or in a zoo can be a confusing experience. While they look like birds in a matter of appearance, penguins do not fly. But if you look up the definition of penguins, they are known as marine birds in zoological descriptions. You must have thought why are penguins birds? Indeed, the question becomes even more significant when you see penguins swimming in the water like fish or waddling on the Antarctic ice like two-legged animals.

Well, in this article we are going to take a look at some of the factors that will remove any doubts in your mind that penguins are birds.

The Role of Evolution

Penguins are found in the Southern hemisphere, mainly in Antarctica. But penguins are also present in the temperate zones of the world such as New Zealand and the coast of Africa. The oldest penguin fossil was found in New Zealand and estimated to be 60 million years old. Penguins evolved from birds that had the power of flight but penguins lost their ability to fly. With time, penguins evolved to survive in the cold and harsh conditions of the Antarctic region.

As birds, penguins had no evolutionary advantage of flying and their wings slowly developed into hard flippers. As the primary food source for penguins in Antarctica such as fish and krill was available underwater, penguins became accomplished swimmers and lost their ability to fly. Penguins move quickly underwater with the help of their flippers and their underwater swimming motion is extremely similar to the flying motion of birds in the air.

Penguins Are Flightless Marine Birds
rock penguin

Another evolutionary change that penguins went through is the development of heavy bones. While most birds have hollow bones that are light in weight and help them to fly, penguins evolved to develop heavy bones to help them swim better. Their flippers are also rigid and bonelike for better movement through the water.


Penguins do not have feathers like other birds as they cannot fly and having long feathers would not be useful for them. Instead, penguins have short and dense feathers that are packed together really close. Penguins can trap air bubbles under their feathers while diving to provide insulation against the cold water.

When exiting the water, penguins vibrate their feathers to release air bubbles and move quickly through the water. Penguins also secrete oil from their glands and coat their feathers in the oil to make them waterproof.

Biological Functions

Penguins lay eggs like all other birds, and both parents play a role in bringing up their chick. Also, like most birds, penguins do not have teeth. They simply swallow their food, and it is digested in their stomach with their stomach acids.

Penguins Share Several Traits With Birds
penguin side view

Penguins also feed their chicks beak to beak by regurgitating food in the mouth of their offspring. Many penguins also eat small rocks and pebbles to help in grinding down the food in their stomach. Also, like other birds, male penguins do not have a penis but their sexual organ is a cloaca that is used for waste emission as well as sexual functions. A less functional reproductive system is another physical trait displayed by birds.  Penguins are also warm-blooded like other birds.


To sum up, there are several traits displayed by penguins that classify them as birds. The ability to fly is not the only condition for a creature to be called a bird as there are several other flightless birds like emus, kiwis, and ostriches. Penguins differ from all these birds because penguins are excellent swimmers and they can bear extremely cold temperatures. Also, there are all sizes of penguins, from small fairy penguins to emperor penguins that are the largest of penguins.

Penguins are unique in every manner from their feeding and hunting to breeding and rearing their chicks. Today, these magnificent birds are endangered because of human intervention in their habitat, growing pollution, and global warming. Efforts are being made to conserve and improve the population of penguins that are considered endangered.

If you have any questions about why penguins are birds, please feel free to ask your questions in the comment section. Our team will do its best to answer all your queries.




Image Source:

  1. rock penguin by frankenstein / Pixabay License
  2. penguin side view by InsaPictures / Pixabay License

I got interested in penguins from a young age and as I grew I realized that penguins are such fascinating birds. I made it a mission to create a website where all information about penguins could be accessed in an easy to read format.

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