Feather

Feathers grow on birds.

They help birds fly. They also keep birds warm. Some feathers are very soft.

These soft feathers trap air. This keeps the bird warm. People use soft feathers in pillows. They also use them in warm coats. Feathers can have many colors.

Some colors help birds hide. Other colors help birds talk to each other. Feathers are very special parts of a bird.

Feathers are special parts of a bird's skin.

They grow from tiny holes called follicles. Feathers help birds fly and stay warm. They also keep birds dry.

There are two main types of feathers. The first are vaned feathers. These cover the outside of the bird's body. They have a main shaft called a rachis. Tiny branches called barbs grow from the shaft. These barbs have even smaller parts called barbules. Small hooks called barbicels zip the barbules together.

The second type are down feathers. These are very soft and fluffy. They do not have hooks. This lets them trap lots of air. Trapped air acts like a warm blanket.

This helps the bird stay warm.

Feathers also come in many colors. Some colors come from pigments. These are tiny bits of color inside the feather. Other colors come from light. Tiny parts of the feather reflect light in special ways. This can make a feather look blue or shiny.

Colors can help a bird hide or find a mate.

Feathers are amazing parts of the skin. They are the most complex structures found on vertebrates. These growths form a covering called plumage. This plumage appears on birds and some dinosaurs. Feathers help birds in many ways. They help with flight and keeping warm. They also help with waterproofing. Colors on feathers can help birds talk to each other. Colors can also help them hide from danger.

Feathers grow from tiny holes in the skin called follicles. These follicles produce proteins called beta-keratins.

These proteins make the feathers very tough. A feather has a main shaft called a rachis. Branches called barbs grow from this shaft. These barbs have even smaller parts called barbules.

Tiny hooks called barbicels zip the barbules together. Down feathers are different because they lack these hooks. This lets them trap air to keep a bird warm.

At the bottom, the shaft forms a hollow tube called a calamus. This is also known as a quill.

People have used feathers for a very long time. In the past, people used large feathers to make quill pens. The word "pen" actually comes from the Latin word for feather. People also use feathers for beautiful things. Some have used them in fashion or for religious items. In the past, hunting birds for pretty feathers was a big problem. It caused some species to become endangered or even go extinct. Today, many feathers come from poultry farming. This includes birds like chickens, turkeys, and ostriches.

There are many specific kinds of feathers. Vaned feathers, or contour feathers, cover the outside of the body.

Flight feathers in the wings are called remiges. Flight feathers in the tail are called rectrices. Some birds have hair-like feathers called filoplumes. These are often hidden by other feathers. Some birds even have stiff bristles around their eyes.

These bristles might help birds catch insects. Other birds have powder down feathers. These create a powder that helps keep feathers waterproof.

Feather colors come from two main ways. Some colors come from pigments. These are tiny bits of color like melanin or carotenoids. Melanin makes colors like brown, black, or grey. Carotenoids make reds, yellows, and oranges. Other colors come from light hitting the feather.

Tiny structures can reflect or scatter light. This creates blue colors or shiny iridescence. Some birds even show colors that humans cannot see. They use these colors to find mates or hide in their homes.

Feathers are complex epidermal growths that form a distinctive outer covering called plumage. This covering appears on all birds and once appeared on some non-avian dinosaurs and other archosaurs. Feathers are considered a complex evolutionary novelty among vertebrates. They serve many vital roles for survival. They aid in flight and provide thermal insulation to keep birds warm. They also help with waterproofing the body. Additionally, feather coloration is essential for communication and protection through camouflage.

Feathers grow from tiny follicles located in the epidermis, which is the outer skin layer. These follicles produce specific proteins known as $\beta$-keratins.

These protein strands are hydrogen-bonded into $\beta$-pleated sheets. They are further twisted and crosslinked by disulfide bridges. This chemical structure makes feathers tougher than the $\alpha$-keratins found in mammalian hair or hooves. While scientists do not know the exact signals that trigger growth, they have found that a transcription factor called cDermo-1 induces feather growth on the skin.

There are several distinct types of feathers categorized by their structure and location. Vaned feathers, also called pennaceous or contour feathers, cover the exterior of the body.

Within these, the remiges are the flight feathers of the wing, while the rectrices are the flight feathers of the tail. Down feathers grow underneath these vaned feathers. They lack barbicels, which are tiny hooks, so their barbules float free to trap air for insulation.

A third, rarer type is the filoplume. These are hair-like structures often hidden near the skin. Some birds also possess rictal bristles, which are stiff feathers found around the eyes and bill.

A typical vaned feather has a specific mechanical design. It features a central shaft called a rachis. Fused to this rachis is a series of branches known as barbs. These barbs further branch into smaller structures called barbules. To keep the feather together, the barbules use minute hooks called barbicels for cross-attachment.

At the base, the rachis expands into a hollow, tubular structure called the calamus, or quill. This quill inserts directly into the skin follicle. In some species, hatchlings possess special natal down feathers called neossoptiles before their adult feathers emerge.

Feather color is produced through pigments or microscopic structures. Most pigments are melanins, which create browns, blacks, and greys. Carotenoids produce reds, yellows, and oranges. Some birds, like turacos, have unique pigments called turacin and turacoverdin. Other colors come from structural coloration. This happens when microscopic structures refract, reflect, or scatter light. This process creates blue colors and iridescence.

In some cases, colors may be altered by secretions from the uropygial gland, also known as the preen gland. This gland also provides oil that may inhibit feather bacteria.

Humans have used feathers for many practical and cultural purposes throughout history. Large feathers from geese were historically used to create quill pens. In fact, the word "pen" is derived from the Latin "penna," meaning feather. Feathers are also used in high-class bedding like pillows and mattresses because they trap heat. Down from geese and eider ducks has great loft, meaning it can expand to trap insulating air. Today, many feathers used in fashion come as a waste product from poultry farming. This includes feathers from chickens, turkeys, and ostriches.

Feathers are deeply connected to the biology and environment of the bird. For example, cormorants have feathers that soak up water to reduce buoyancy, helping them swim submerged. Some birds, like herons, use powder down feathers to help waterproof their plumage. Color patterns are also vital for social systems. Striking color differences are often part of sexual dimorphism, helping birds select mating pairs. Even the way feathers are distributed on the skin, known as pterylosis, helps scientists understand evolutionary relationships between different bird families.