Chicken Anatomy: A Complete Visual Guide

Chickens are very different to humans in their anatomy and construction.

Perhaps the biggest difference is their wings and their ability to fly.

Without some very specialized modifications chickens would not be able to fly, even with wings!

The respiratory system is delicate too. You should never let a child hold a chicken too tightly as it is easy to suffocate a chicken in this manner.

Understanding the basic anatomy of your chickens is important. You do not have to know it in depth, but knowing the basics can help you understand how your flock functions.

Keep reading to learn the basics of chicken anatomy…

Chicken Anatomy

Chicken Anatomy

The anatomy of chickens is quite similar to the human anatomy in several ways, but totally different in others.

Basic functions of locomotion, eating, vocalization and sexual reproduction are all similar but do have certain adaptations and differences to make it all work.

We can use the chicken eye as an example.

While a chicken is foraging for food, she also has to be on the lookout for predators. Her eyes are placed on the sides of her head to increase the overall visual field and while one eye is focused on the ground looking for food, the other eye is constantly scanning the environment for threats. Each eye is independent of the other.

The anatomy of bones and wings are also a survival tactic.

Wings allow the bird to successfully fly up and away from a land based predator. Six to 8,000 thousand years ago, jungle fowl (chickens’ ancestors) were living in areas of dense vegetation. They could fly well but not very far. However over the years as humans domesticated some of these fowl and started to cross breed them, their ability to fly diminished.

Modern breeds such as Orpingtons would be lucky to get off the ground for any appreciable distance and this extends to many of the larger breeds.

Common Chicken Parts

Chicken Comb

The chicken has a lot of interesting parts that we really do not think about too much. The following is a quick look at some of the more fascinating areas of the chicken.

Common Chicken Body Parts
Comb and Wattles The comb, in combination with the wattles, is the chicken heating and cooling unit. When a hen gets too hot, she will lose heat through her comb and wattles. When she is cold she can shut down the blood supply to conserve heat. It is red and plump on healthy chickens.
Sickle Feather Only roosters have sickle feathers. These are the long arching feathers found in their tail – they are for adornment only and serve no practical purpose.
Saddle In hens the saddle area has much the same type of feathering as seen anywhere on her body. With roosters however, their saddle feathers are long and flowing on either side of the tail feathers. This is to attract the ladies and can be considered a secondary sexual characteristic.
Shank The shank of the chicken is the long upright area of the leg between the hock and the foot. Spurs can grow from this area.
Spur All chickens can grow spurs, but usually only the males do. They grow on the back of the shank and can do some serious damage!
Hock The hock is the upper part of the leg between the drumstick and the shank.
Hackle Both sexes have hackles and hens will raise their hackles to look more intimidating to possible predators. The boys hackles are a secondary sexual characteristic, they are usually longer than the females’ and flow down into the body of the bird.
Fluff The presence of fluff feathers under the main plumage is to keep the chicken warm. However they can also be fluffed out to make them appear bigger than they are to a predator or to keep other chickens away.
Tail Feathers In the female the tail feathers are short and strictly utilitarian, they help her to balance and can assist in the takeoff phase of flight. With roosters the tail is a secondary sexual characteristic and is much more eye catching to the ladies.
Cloaca The cloaca can be found at the back of the chicken. This is where the reproductive system ends and the egg is expelled or laid into the nest.
Ear Tufts The little round group of short plumes that make up the ear tuft cover the auditory canal, an open round hole that is the hen’s ears. It is thought that the short plumes that form the tuft concentrate the sound waves so that the chicken has exceptional hearing.

Chicken Bone Anatomy

Chicken Bone Anatomy

The bone anatomy of any creature is a stunning feat of engineering; however, it is even more impressive with birds when you consider what their skeleton actually does.

All bones are made from a protein known as collagen, and it is calcium that makes them hard.

Most vertebrates have a skeleton that consists of one type of bone that serves several purposes. However, chickens actually have two different types of bones that serve very different purposes.

Bone Type 1: Medullary Bones

These bones are important areas of calcium storage.

They include the ribs, shoulder, and leg bones. They store a huge amount of calcium which is used for bone health and growth and strong egg shells. A full 47% of calcium required for shell formation comes from the bones. The remainder comes from a hen’s diet and feed.

Should the amount of calcium in the bones fall below a certain level then the hen will start to lay soft shelled eggs. If the calcium depletion continues, she will stop laying altogether to protect her bone health. This is known as cage layer fatigue, the chicken version of osteoporosis.

Bone Type 2: Pneumatic Bones

The second type of bones are referred to as pneumatic.

Examples of this type of bone are the skull, keel, pelvis, and lower back.

These bones are hollow and the center of the bone contains air and a network of fine mesh which gives the bone a honeycomb appearance internally.

Pneumatic bones are connected to the respiratory system via the air sacs which means these bones are lightweight and air can flow through these bones and interconnect with the air sacs. The overall effect is to make the chicken light enough to fly.

Chicken Wing and Feather Anatomy

Chicken Wing and Feather Anatomy

With the majority of birds the wings are used to help them fly.

Their wing and chest muscles are well developed and the body is streamlined.

Some birds fly to hunt, whereas others are ground feeders and some are divers. All of these groups have specialized muscles for the tasks of life.

As for chickens, most breeds today are virtually flightless thanks to humans selectively breeding them. Their ancestors were able to fly up into trees to escape predators, but they were never birds that flew long distances because of a lack of endurance.

The longest recorded flight of a chicken was just about 300 feet and lasted 13 seconds.

Bantams are usually still able to fly but only for short distances in what is known as a burst flight.

The shape of their wing is short and rounded, indicating that the wing is used for quick take offs rather than gliding.

This brings us to the feathers.

Feather are incredibly complex yet simple.

They are mostly made from mostly keratin (90%) and are colored by a combination of melanin and porphyrin.

There are several types of feather, and each of these types has a specific purpose:

  • Contour: As their name implies this type of feather conveys the general outline of the chicken.
  • Flight: These feathers let them fly. This group is further divided into primary and secondary flight feathers.
  • Down: This is the under fluff that keeps out cold air and keeps them warm.
  • Semi-plume: These feathers add another layer of insulation to the body.
  • Filo-plume: These unusual feathers attach to nerve endings and are thought to be a tool for proprioception, their sense of their own bodies
  • Bristles: Mostly found on the head around the eyes. Their exact use is unknown but they are thought to be used as a sensory tool.

The actual structure of the feather varies depending on the feather itself.

Individual strands of the feather are interlocked to provide strength and form. The feathers are linked together by barbules which are small hooks that latch onto the next strand. This forms a strong semi-rigid surface to the feather.

Silkies and Frizzles lack these barbules which gives their feathers their unique appearance.

Summary

After reading this article you should understand chicken anatomy.

Their anatomy is complex but we have tried to simplify it here to give you a basic understanding of how it works.

Bone structure, wings and feathers, and the respiratory system all help chickens fly. This article should give you a basic understanding of how the respiratory system links to the bones and helps to enable flight and why bone health is important for egg laying.

The ability of chickens to fly has been severely diminished over the years and this has reduced their ability to escape from predators.

Because of this, you need to keep your chickens as safe as possible from the host of predators that like chicken dinner.

If you already have chickens then you will probably know that certain members of your flock like nothing better than to fly over the fence to check out the neighbor’s yard. This can get them into serious trouble at times, so if you do have an adventurous soul among your flock you may have to resort to wing trimming.

Also, remember that their legs and wings can get broken if not handled properly. Never pick up your chickens by the feet or wings as this can cause injury and pain.

Which part of a chicken’s anatomy interests you the most? Let us know in the comments section below…

Chris Lesley Bio Picture
Chris Lesley has been Raising Chickens for over 20 years and is a fourth generation chicken keeper. She can remember being a young child when her grandad first taught her how to hold and care for chickens. She also holds a certificate in Animal Behavior and Welfare and is interested in backyard chicken health and care.