Your cockatiel’s body is essentially very similar to that of a mammal. Both have skin, bones, muscles, sensory organs, and respiratory, cardiovascular, digestive, and nervous systems, although the various systems work in slightly different ways.
Skin
Your bird’s skin is difficult to see, since your cockatiel has so many feathers. If you part the feathers carefully, though, you can see thin, seemingly transparent skin and the muscles beneath it. Modified skin cells help make up your bird’s beak, cere, claws, and the scales on her feet and legs.
Birds cannot perspire as mammals do because birds have no sweat glands, so they must have a way to cool themselves off. On a warm day, you may notice your bird sitting with her wings held away from her body, rolling her tongue, and holding her mouth open. This is how a bird cools herself off.
Watch your bird carefully on warm days because she can overheat quickly, and she may suffer from heatstroke, which requires veterinary care. If you live in a warm climate, ask your avian veterinarian how you can protect your bird from this serious problem.
Musculoskeletal System
Next, let’s look at your bird’s skeleton. Did you know that some bird bones are hollow? These are lighter, making flying easier, but it also means these bones are more susceptible to breakage. For this reason, you must always handle your bird carefully!
Another adaptation for flight is that the bones of a bird’s wing (which correspond to our arm and hand bones) are fused for greater strength. Birds also have air sacs in some of their bones (these are called pneumatic bones) and in certain body cavities that help lighten the bird’s body and also cool her more efficiently.
Parrots have ten neck vertebrae, compared to a human’s seven. This makes a parrot’s neck more mobile than a person’s (a parrot can turn her head almost 180 degrees). This gives the parrot an advantage in spotting food and predators in the wild.
During breeding season, a female bird’s bones become denser to enable her to store the calcium needed to create eggshells. A female’s skeleton can weigh up to 20 percent more during breeding season than she does the rest of the year because of this calcium storage.
Respiratory System
Your bird’s respiratory system is highly efficient and works in a markedly different way from yours. Here’s how your bird breathes: Air enters the body through your bird’s nares, then passes through her sinuses and into her throat. As it does, the air is filtered through the choana, which is a slit that can easily be seen in the roof of many birds’ mouths. The choana also helps clean and warm the air before it goes further into the respiratory system.
After the air passes the choana, it flows through the larynx and trachea, past the syrinx, or voice box. Your bird doesn’t have vocal cords like you do; rather, vibrations of the syrinx membrane are what enable birds to make sounds. So far it sounds similar to the way we breathe, doesn’t it? Well, here’s where the differences get bigger. As the air continues its journey past the syrinx and into the bronchi, your bird’s lungs don’t expand and contract to bring the air in and push it out. This is partly due to the fact that birds don’t have diaphragms, as people do. Instead, the bird’s body wall expands and contracts, much like a fireplace bellows. This action brings air into the air sacs mentioned earlier as part of the skeleton. This bellows action also moves air in and out of the lungs.
Although a bird’s respiratory system is extremely efficient at exchanging gases in the system, two complete breaths are required to do the same work that a single breath does in people and other mammals. This is why you may notice that your bird seems to be breathing quite quickly.
Nervous System
Your cockatiel’s nervous system is very similar to your own. Both are made up of the brain, the spinal cord, and countless nerves throughout the body that transmit messages to and from the brain.
Cardiovascular System
Along with the respiratory system, your bird’s cardiovascular system keeps oxygen and other nutrients moving throughout her body, although the circulatory path in your cockatiel differs from yours. In your cockatiel, blood flowing from the legs, reproductive system, and lower intestines passes through the kidneys on its way back to the general circulatory system.
Digestive System
Your bird’s body needs fuel for energy. Birds’ bodies are fueled by food, which is where your bird’s digestive system comes in. The digestive system provides the fuel that maintains your bird’s body temperature—which is higher than yours.
(The first time I bird-sat for friends, I worried about their cockatoo’s seemingly hot feet. But when another bird owner told me that birds have higher temperatures than people, I stopped worrying about the bird’s warm feet.)
Your cockatiel’s digestive system begins with her beak. The size and shape of a bird’s beak depend on her food-gathering needs. Compare the sharp, pointed beak of an eagle or the elongated bill of a hummingbird with the small, hooked beak of your cockatiel.
Because cockatiels primarily eat seeds and other plant materials, their beaks have developed into efficient little seed crackers. Look closely at the underside of your bird’s upper beak, if you can. It has tiny ridges that help your cockatiel hold and crack seeds more easily. A parrot’s mouth works differently than a mammal’s. Parrots don’t have saliva to break down and move their food, as we do. After the food leaves your bird’s mouth, it travels down the esophagus, where it is moistened.
The food then travels to the crop, where it is moistened further and is passed in small increments into the bird’s gizzard. Between the crop and the gizzard, food passes through the proventriculus, where digestive juices are added. Once in the gizzard, the food is broken down into even smaller pieces. The food next travels to the small intestine, where nutrients are absorbed into the bloodstream. Anything that’s left over travels through the large intestine to the cloaca, which is the common chamber that collects wastes before they leave the bird’s body through the vent. The whole process from mouth to vent usually takes only a few hours, which is why you may notice that your bird leaves frequent, small droppings in her cage.
Along with the solid waste created by the digestive system, your cockatiel’s kidneys create urine, which is transported through ureters to the cloaca for excretion. Unlike a mammal, a bird does not have a bladder or a urethra.
