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Why Do Birds Have Feathers?

Pushpa Duddukuri
Feathers protect birds from the elements. But you may wonder, why feathers? Why not fur, which more or less carries out the same function of thermoregulation? The answer lies in the evolutionary history of birds.

Pingu's Feathers!

Since all birds have feathers, penguins are no exception. Their feathers are short, densely packed, and provide a waterproof outer-covering. Whereas, the inner layer of the feathers keep the penguins warm even in freezing temperatures.
Every continent has a diverse range of birds with beautiful and varied plumage. You probably won't believe me if I tell you that birds and dinosaurs have the same ancestors. Yes, birds―the creatures that flutter their wings and chirp aloud early in the morning―have come a long way from terrifying and dominating prehistoric Earth.
Birds are quite unique, not only because of their ability to fly, but also due to their defining feature―feathers. So, why do birds have these soft plumes? The obvious answer to this, is for flight. The plumage enables the birds to fine-tune their ability to fly to such a degree that no other organism has been able to match it.

Our feathery friends have a specific lifestyle, and their plumes play an important role in meeting their dietary and other needs.

The Function of Feathers

No doubt, feathers are one of the most beautifully designed structures in the living world. They have multiple uses, some of which are mentioned below.


Even though the use of feathers for flying is quite evident, they were not evolved for this function. It was an adaptation that underwent modification in the later stages of avian evolution.


Their main function is to provide thermoregulation. Whether it is biting cold or scorching hot, the feathers act as a protection against the harsh elements of nature. The feathers fluff up and catch insulating air to protect the bird during cold weather; whereas in summer, the feathers flatten against the body, and these trapped pockets of air are removed.

Protection from External Elements

Feathers are also pretty handy during the rains, as they have waterproof properties and act as a raincoat. Thus, keeping the bird dry. Some birds also have a preen gland, which secretes an oil, and acts as an extra layer of protection against the rain. It suppresses the growth of bacteria and fungus on the body.

Touch Sensors

A recent study published in Animal Behaviour  revealed that birds use their feathers to sense their surroundings, just like a cat uses its whiskers. Even though the feathers do not have nerves, they are connected to the area where the nerves are attached. When the nerves get stimulated, birds change the feather positions and their posture.

Other Functions

Some birds, like herons, hunt by making an umbrella over their head with their feathers, which aids in catching fish. The feathers of hummingbirds help them in pollinating flowers. There are birds who use their own feathers to create a nest for their offspring. On the other hand, certain birds consume their own feathers, in order to aid their digestion process. The feathers line the digestive tract of the birds and protect them when they eat sharp fish bones.

Theories Related to Evolution of Feathers

So, where did the feathers come from in the first place? Dinosaurs, you say? But then, there were some dinosaur bones discovered in China, which turned out be of a flightless creature. Moreover, most of us know that the flying pterodactyl was a featherless dinosaur. What was the purpose of feathers for a flightless creature? All these questions and the evolutionary stages between these dinosaurs are confusing enough to stump a paleontologist. But here, we are going to explain the evolution of feathers to our best ability.
As you may know, feathers are an advanced adaptation of the integument (skin). A theory, known as the Arboreal Hypothesis, suggests that the ancestral birds took to flying by jumping of trees. However, this theory lost favor in paleontology circles when some fossils of theropods were discovered in China.
There was another theory that suggested the existence of protobirds,which ran fast and leaped from the ground to catch elusive preys,like insects. In order to do this,protobirds developed the ability to raise their body in the air and land safely on the ground. This gradually led to the flapping of the wings, and with time,the protobirds soared in the skies.
Another theory that is doing the rounds nowadays is that, the evolution of feathers happened not for the purpose of flight or insulation, but for the display of power and sexual dominance. According to this hypothesis, the feathers were first formed to be displayed. This theory got a great boost in 2009, when scientist discovered microscopic sacs inside the feathers of theropods. These sacs, called melanosomes, are similar to the structures present in the feathers of living birds.
Feathers are, no doubt, novel structures which have a rather mysterious evolutionary origin. It is quite a difficult process to reconstruct how they evolved and more importantly, why at all?