HAMILTON & DISTRICT BUDGERIGAR SOCIETY INC.

THE REPRODUCTIVE OR GENITAL SYSTEM


The Male:
The male bird possesses two testes or testicles of roughly equal size. They are ovoid in shape, vary considerably in colour, but are usually whitish. They are situated side by side and slightly apart in the dorsal part of the body cavity near the anterior ends of the kidneys. There is great seasonal variation in the size of the testes, whilst in immature birds they are often too small to see with the naked eye. They are largely made up of coiled tubes in which the tadpole-like spermatozoa are produced. The sperms mature in a ridge on the upper and inner face of the testis called the epididymis. From here a wavy tube and temporary store, known as the vas deferens, carries the sperms when required to its opening on a little hump in the lining of the urodaeum which is a section of the cloaca. In some birds, such as ducks and the ostrich, the hump or papilla is developed into a grooved penis. It is interesting to note that the testes do not descend into a pouch or scrotum in birds as they do in mammals, where they are kept at a temperature lower than that of the body. In common with their reptilian ancestors, the body temperature of birds fluctuates; it is believed that when it falls at night, sperm production can then proceed. Sperm-generating cells exist in quite young chicks, but only produce sperm when puberty is reached. The testes also produce a chemical messenger or hormone, known as testosterone, in addition to spermatozoa. This hormone, manufactured by small groups of glandular cells dotted about between the sperm-producing tubules, passes directly into the bloodstream and reaches all parts of the body.

Two Budgies in mating position.

Testosterone generates and maintains the secondary sexual characteristics, such as the typical male head and body shape of a particular species, its posture, voice, plumage and colour. It is also responsible for the increase in size of the fleshy wattles and cere of some species. The sperm and testosterone output depends upon secretions coming from the pituitary gland in the form of two other hormones. The output of the pituitary gland is dependent on the bird's age, nutrition, and the number of hours of daylight, this last factor determines the seasons for breeding. Testes are inactive in the winter months, being very small and containing no developed sperms. In spring, the size of the testes increases many times. In the house sparrow the enlargement is from a pinhead to as much as 1.25 cm., or about a fifty-fold increase. Removal of the testes results in gradual loss of most of the secondary sexual characteristics, and produces a neuter bird.

In appearance, neuters or capons as they are called in domestic fowls, are intermediate between males and females. They tend to be more placid, put more weight on their basically masculine bone structure, and show none of the seasonal sexual behaviour patterns. Injection or implantation with the female hormone into a normal male has a similar effect, although some male characteristics may still remain. This process of chemical caponization using the female hormone is used to speed the fattening of poultry for the table, whilst eliminating the objectionable early morning crowing and fighting. Injection or implantation of the male hormone into a surgically caponized bird restores all the external signs of masculinity, even resulting in the "treading" or attempted mating of females, although of course fertilisation is impossible. In a normal male such injections may produce an abnormal assertiveness, a tendency to mate several females, and even tread males.

The Female:
The adult female has only one active gonad, the left, the right gonad is usually rudimentary. This gonad is called the ovary. Sometimes hawks possess paired ovaries but only a left oviduct, but this is very unusual in other birds. The ovary develops from a tiny granular mass, as seen in the young female chick, into a bunch of different-sized cyst-like structures or follicles which contain the ova or undeveloped eggs at puberty. This in the wild state generally coincides with spring. The ovary lies under the anterior end of the left kidney. Its component follicles are loosely attached to one another by connective tissue. The ovary produces female hormones or oestrogens in addition to its primary function to make ova--the eggs or female germ cells. Oestrogens stimulate the female characteristics of plumage, colour and voice. The ovary, like the testes, decreases in size in winter when the hours of daylight are short, and then enlarges again when the lengthening days of spring stimulate the pituitary gland. As the ova enlarge, they form grape-like clusters, rupture from their follicles and drop into the funnel-shaped opening or infundibulum of the oviduct.

Intermittent contractions of the oviduct similar to those which occur in the intestine, propel the ovum which is now an egg yolk, down the oviduct. Its progress is also facilitated by the presence of cilia lining the inside of the oviduct. In its slow, spasmodic journey the yolk gathers up layer after layer of coverings which form the "white" or albumen, and finally the skin or egg membranes. During the last part of its journey, the egg receives the minerals which form the shell. It is at this stage that the pigments are deposited which give the characteristic colours and markings to the shells of many species. The presence of oestrogens in the adolescent bird is essential for the widening of the pelvic outlet to enable eggs to be passed, this being one of the numerous adjustments which the female must make in order to prepare for egglaying. At this time, calcium, magnesium, and phosphates are also withdrawn from the bones. The intestine, liver and pancreas must digest and temporarily store vastly increased amounts of proteins, sugars, fats, vitamins and minerals. After a brief respite during incubation of the eggs, the female must feed the young. The pigeon and budgerigar produce highly concentrated crop or stomach milk respectively for this, in others, regurgitated or partly digested food is given. The growth rate of pigeon and budgerigar chicks is phenomenal, they increase as much as six-fold in size in the first three weeks of age. By five to six weeks, when nestlings are about to leave the nest, the youngsters of many species are almost as large as their parents. Feeding the young places a considerable strain on the parent birds, which usually lose weight during the rearing period.

For reproductive behaviour you can read the below articles.
Choice of Mate.
Rejection of Mate.
Courtship and Mating.
Mating new birds.

E-Mail: berniehansen@sympatico.ca

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Hamilton & District Budgerigar Society Inc.