Birds are unique among flying animals in that they make wonderful pets. Their physiology also makes them interesting. No other animals have feathers, and in many other ways, bird anatomy differs from that of all other living beings. To ensure your bird remains healthy, as well as to distinguish when it isn't healthy, you need to understand the primary features of bird anatomy and recognize deviations from the norm.


Your bird's skeleton is thin and much lighter than a mammal's, and this characteristic is one reason she can fly. Unfortunately, this characteristic also makes her susceptible to fractures. The skull, too, is very thin, so your bird is extremely vulnerable to injuries if she collides with a hard object while in flight. Fortunately, she has extraordinary vision to compensate for this problem. If you were to examine a bird's skull, you would find it has unusually large eye sockets to make room for the large eyes that help her see so well.


The eyes are located on the side of the head. This allows your bird to see things on each side as well as in front (monocular vision). Some birds have a 300-degree range of vision without turning their heads! Other birds have eyes further back on their heads, so they can even see things behind them. Bird eyes are flatter than human eyes. This flatness allows your bird to have a larger area in focus at one time.

Birds who look for food during the day have excellent color perception. A hummingbird can spot a flower from over one half mile away. Birds who hunt at night see colors less vividly, but can see well in low light.

Regardless of variation in structure and use, the eyes of all healthy birds are bright and alert, and they should be free of discharge, redness and swelling.


The lightness of your bird's head derives partly from the thinness of her skull and partly from a complete absence of teeth. Scientists have evidence that primitive birds in the Jurassic Period (approximately 200 million years ago) had teeth and preyed on insects. Since birds today have extremely strong jawbones and therefore don't need teeth, birds may have shed their teeth through evolution to become lighter for flight. Today's birds have what is known as a horny sheath (rhamphotheca) that covers the upper and lower bills. This sheath is constantly replaced as is it worn down.

Birds have good hearing, but you might not know it from looking at your bird's head. The outer opening of the ear (auditory meatus) is hard to find because it's covered with feathers.


Bird bills come in several different shapes and sizes, but they all serve the same purpose - to provide a method of eating. Birds that eat nectar, for example, have narrow, pointed bills. Short, stout bills enable other birds to crack open seeds and eat kernels. Insect- and berry-eating birds have long bills with which they turn over leaves, gather berries and catch insects. Some birds may suffer from a condition known as an overgrown beak, in which the upper or lower beak continues to grow to a length that impedes proper eating. These birds must have their beaks trimmed on a regular basis, sometimes as often as once a week. Most birds avoid this problem by regularly chewing on branches or stones.

Back (Vertebral Column)

If you could look at the bones of your bird's back, you would find that some of the vertebrae are fused together. This characteristic helps distribute body weight evenly, providing your bird with more stability when she walks.


The unique structure of your bird's legs helps her move more gracefully on the ground. Tight leg muscles hold each leg closely to the body. Although this characteristic makes the thigh bone (femur) less mobile than in mammals, it also helps shift your bird's center of gravity, making it easier for her to move on the ground.

Bird legs are covered with scales, much like the legs of a lizard. The foot has a rear-facing structure, which aids your bird in perching.


A special wing structure prevents birds from crushing their chests. Special bones (such as the keel of the sternum, to which the flight muscles are connected) prevent this from happening. When buying a bird, make sure the keel is not too prominent, as a prominent keel could signal illness.

The wishbone is located in the wing structure and provides reinforcement. In fossils, you can tell from the presence of a wishbone that the bird once was a flying bird. The wing bones are porous, which makes them light.


The crop is part of the bird's digestive tract. It stores food, so that if she can't find enough to eat, she has some food in reserve. Some bird species, such as pigeons, produce "crop milk," with which a mother bird nourishes her chicks for the first few days of life. A bird's total digestive tract consists of the liver, intestine, pancreas and stomach.

Vent and Droppings

Your bird does not have what we know of as a bladder. Her body, like that of a human being, produces uric acid, but instead of being excreted as urine, the uric acid is reabsorbed into the body, where it is formed into a white, semisolid ball. Normal bird droppings (fecal matter) are expelled from an opening called the vent. Healthy fecal droppings are usually dark green, semisolid and tubular in shape. If you bird is ill, her droppings may look like pea soup.

Near the vent is the uropygial gland, which produces the fatty acids, fat, wax and Vitamin D that your bird uses for preening her feathers. Preening is a sign of good health.


Birds have several different types of feathers. Flight feathers, which are found on the wings and tail, keep birds in the air during flight. Feathers on the body, or body plumage, are flat and lie close to the body to provide warmth and protection from rain.

Once a year, your bird may begin to look pretty ragged. She is probably molting - a normal, annual process in which she sheds her feathers and grows new ones. Molting can occur at different times of the year, and the timing may be affected by mating season or by temperature and light changes that signal a change of season.

During molting, be sure to provide your bird with plenty of food. Molting takes a lot of energy, and extra nutrients are needed so your bird can produce the new, colorful feathers.


Your bird's lungs have openings at both ends. In mammals, the lungs have only one opening, at which air is both taken in and expelled. Your bird's special lung structure allows her to have fresh air in her lungs even when she is breathing out. Bird lungs are much more efficient than ours at getting oxygen out of the air, which aids in flight. A healthy bird does not wheeze. Wheezing indicates illness.


The toes and claws enable your bird to perch, so it is important to make sure they do not get too long or become curled, wavy or hooked. A bird's toes and claws have evolved since primitive times. Scientists have evidence that birds may actually have had claws on their wings at one time, which helped them move around in the trees.


Bird tongues come in a variety of sizes and shapes and have one purpose, which is to aid in feeding. Birds with long tongues, like woodpeckers, actually store their tongues over their skulls. Sometimes the end of the tongue rests in the nostril. The tongue has many blood vessels. If you bird slits her tongue, it is a medical emergency.