INSIDE THE BIRD

We have been talking about fresh air, good food and proper partners. When we have a look inside a bird, many "whys" will give us answers. Let us have a quick look inside the bird.

SKELETON

The skeleton is constituted from organic proteins, and the inorganic materials calcium and phosphorus. The skeleton has three important functions. It must give as little resistance as possible in the air during flight. It must be light but strong, and it must give protection to the internal organs, such as the heart, lungs, liver, stomach and many more.

In order to make the bird as light as possible, most bones are hollow and filled with air. In parts of the skeleton which require added strength, such as the wings, the inside of the bones have built-in bony "props" which increase strength, without increasing the weight too much. The weight of the skeleton is only 1O% of the total body weight.

A unique feature of the bird skeleton is that the vertebral column, consisting of the cervical, thoracic, lumbar and tail vertebrae, is partly fused together. Together with the large breastbone, the attached ribs and the pelvic bone, this forms a strong and efficient basis for flight.

In order to compensate for the loss of body movement, the neck has 14 vertebrae, so arranged that the head can be turned through an angle of 180 degrees.

If we take a bird in the hand, we can feel the keel of the breastbone. As the breastbone is necessary to give the needed strength to the skeleton, enough room is left for the flying muscles, which lie, between the breastbone and the upper wing bone.

The flying muscles which operate the down beat of the wings are especially strongly attached to the breast bone, while those that operate the upward beat are less sturdy and the area of attachment is moderately smaller. The flying muscles make up about 25% of the total body weight.

LUNGS

Bird lungs are relatively small and not as elastic as those of a mammal. They consist of a number of air canals, which break up into hair-like vessels, richly supplied with blood. The lungs sit close to the vertebral column, roughly in the center of the body and are attached to five pairs of air sacs. These thin-walled sacs fill up space between the organs and thus help to protect them. The air sacs are distributed in pairs through the body and the rear most pair is the largest.

A flying bird contracts its muscles strongly by the downward stroke of the wings. This places the inner body cavities under pressure, and the air from the air sacs is expelled via the lungs. The upward swing of the wings expands the breast muscles, creating the opposite effect, and air is sucked back into the sacs via the lungs.

There are few blood vessels in the air sacs and little oxygen is taken up there. The lungs however, have a rich blood supply, especially in the hair vessels, where oxygen is absorbed and carbon dioxide is given up. When the bird is at rest, the ribs are moved by muscles of the body cavity, which causes air to be sucked into and expelled from the air sacs, so that gas exchange can take place.

At rest, a bird, for example a pigeon, respites about 30 times per minute; this can increase to about 400 times per minute during intense activity.

HEART AND BLOOD CIRCULATION

The heart is a strong muscle, which performs as a pump. It pumps the blood, which transports food and oxygen, to all parts of the body. The heart is divided into four parts consisting of a left and a right compartment, which are not directly connected with each other. The left compartment sucks in oxygen rich blood from the lungs, and pushes it to all parts of the body and organs.

Here, the blood gives up the foodstuffs and oxygen, and the oxygen-poor blood is brought back to the right compartment of the heart, from where it is pumped to the Iungs where excess carbon dioxide is given up.

A bird's heart pumps on average, 240 beats a minute. This may well increase to 400 beats per minute, during moments of intense activity.

THE LIVER

The liver is the largest organ in a bird's body. It is a very important organ with several essential functions:

Many birds do not possess a gall bladder. The gall is passed directly from the liver into the intestine and is produced constantly. If a bird goes for a time without food, its green droppings will consist almost entirely of pure gall.

THE KIDNEYS

Waste materials in the blood are filtered out by the kidneys and converted into urine, which is then passed to the cloaca for disposal. Urinary fluid is taken back into the bloodstream and the waste materials remain as a semi-solid material, which is pass as the white part of the droppings. Many bird fanciers think that this white substance is calcium but it is nothing more than crystallized urine.

THE FEMALE SEX ORGAN

The last organ we need to talk about in short is the female sex organ, which consists of an ovary and an oviduct.

There are about 1,000 to 1,600 egg follicles in the ovary. These are surrounded by a blood rich membrane, in which the follicles are supplied with food and can grow. When an egg follicle had grown into an egg cell, the membrane splits and the egg cell is deposited at the entrance to the oviduct. At this point, the egg cell can be utilized cell in about three hours. Then, a pair of egg membranes are laid around the albumin in about another hour, and in 21 hours, the almost complete egg passes into the "shelling" department. Then the egg passes to the entrance of the cloaca.

The total egg is produced in about 25 hours. The time difference between the laying of the first and second egg is around 43-44 hours. If the hen has no ripe egg follicles, she can still be fertilized by the cock, even as much as 14 days before the follicle ripens. This is probably so that in later matings, the egg cell has a better chance of being fertilized. The older sperm cells are somewhat slower in movement. The female can also be fertilized between the laying of the first and second egg.

With infections of the ovary, which can be caused by stress due to various external factors, the production of the eggs can stop. At times, it is difficult to discover the precise cause. Sometimes it can happen that an egg is produced without a shell (soft-shelled egg). The cause here is possibly that the bird is too fat; fat germs around the oviduct applies pressure which means that normal shell formation cannot take place.

Reprinted by Pretty Birds from Pet Business Magazine by Dr. Matthew M. Vriends

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