The testes show variations in size and structure, depending to some degree on the bird's maturity, the time of year and the opportunities for breeding. Inflammatory changes are uncommon except as part of a generalised infection or other disease. A shrivelling-up or atrophic degeneration of both testes occurs in starvation and after certain hormonal disorders. Only one testis may be affected under some circumstances. Tumour formation and damage by infection, such as a septicaemia, can inhibit sperm production and make the bird temporarily or permanently sterile, although this seldom occurs. Sterility is more likely to result from damage to the genital tract in certain deficiency diseases or hormonal imbalances. The testes in budgerigars are one of the commonest sites for tumour formation, but other species are relatively little affected. Since the testis has two major functions, namely to produce sperms and to produce the hormones which create the sexual urge or libido, neoplastic lesions can seriously affect fertility. Most cases of sterility are, however, attributable to the female. Atrophy of both testes is occasionally seen, with total loss of sexual desire and secondary male sex characteristics such as plumage colour, and it is assumed that the pituitary or other endocrine dysfunction is responsible. Chronic orchitis or inflammation of the testes, seems to be quite rare in birds. Attempts to tread other males, especially by young birds, can be assumed to be normal, especially if the assaulted male is small, dull-coloured, non-assertive or deformed in some way.

From the testis, sperms pass through the epididymis in which they mature and are prepared for fertilisation and then into the vas deferens. The latter is rarely affected by disease except if its lumen is occluded by swelling from inflammatory changes or if it is involved in abdominal tumours, when only one vas deferens may be affected. The usual site for obstructions of these types is at the emergence of the ducts into the cloaca near the sexual papilla or rudimentary penis, inflammatory changes here usually being brought about through contamination by the faeces.

The age of sexual maturity may be reached in the off-season winter months, but it is only in the normal breeding season that the testes become fully functional. These seasonal changes depend on the length of daylight and for birds in the temperate climates this is usually the summer months. Some domesticated species such as the budgerigar, bred for generations in captivity, can mate and produce young in the winter months. This unnatural state of affairs, which is utilised by some breeders to take advantage of the higher prices commanded at this time of year, brings its attendant troubles. Several years ago weakly youngsters, French moult, and a high proportion of dead-in-the-shell chicks and deaths among nestlings were some of the penalties for this unwise practice, but today with correct conditions and diet most are very healthy. By supplying extra light or artificial daylight, to lengthen progressively the shortening winter days, it is possible to stimulate the pituitary gland and induce breeding out of season in several species of birds.

Libido, the urge to court and mate, is a strictly seasonal affair with male birds of most species. In many species in the wild state courtship starts on almost exactly the same date each year, although a particularly cold period just before this time may cause some delay. In the case of captive, wild birds brought from other climates, it is not surprising that even in the most natural of planted aviaries breeding is often extremely difficult to achieve. Breeding a species successfully for the first time in captivity is an attainment of which to be proud, and a tribute to the breeder. In addition to luck and much patient observation and study of the habits and diet of the birds in captivity it is also necessary to apply knowledge based on the habits of the species in the wild. Many of the rarer species have of course not yet been bred, in spite of many attempts, and it may be wondered why this should be so. In the first place, the selected pair stubbornly refuse to mate and no sexual interest is shown. This may be because the birds are in a perpetual state of fear in their new surroundings and cannot escape beyond the wire netting from threatened danger. In many cases, the effects of unsatisfactory methods of transport when hundred of birds are crammed into boxes like sardines in a tin, must have a considerable and long term effect on some individuals. Incorrect diet, violent changes of temperature and humidity, and other privations increase susceptibility to infections and parasitic burdens, and may permanently impair health and fertility. Birds with the best chance of surviving to breed are those which are flown rapidly from source to ultimate destination, or those brought over by ship singly or in small numbers by an attentive bird-lover who acclimatises the birds gently to human handling, a modified diet and to their new environment. The absence of this type of attention is probably the most important reason for loss of libido in the less-studied, delicate and rarer species. In species which have been bred for generations in this country such as budgerigars and the hardier species of parakeets, lovebirds, Java sparrows and pigeons, these factors are less important. In such species, although goad health is still a major factor, free accessibility to daylight and exercise, an adequate food supply and freedom from persecution by other aviary birds and marauders, play an important part in successful breeding. Sufficient space, lack of disturbance and a correct diet are the three most important inducements to breeding. Other causes of sterility are anatomical defects which prevent the production, maturation, passage or ejaculation of active living sperms. Orchitis, testicular degenerationís, tumours, obstructions or alterations in the chemical constituents of the fluid portion of the ejaculate may be at fault. In poultry, ejaculation can be produced by electrical stimulation, but so far this technique has not been developed for the smaller cage birds; consequently an ejaculate cannot readily be obtained for microscopic or other examination. A practical means of determining fertility in a male which is seen to mate satisfactorily is to mate the cock with a series of females. If all hens lay infertile eggs then the male is likely to be sterile. Unfortunately this test is not possible with birds which pair with one hen for a season or for life.

In males, if mounting or being mounted by members of the same sex persists, it can be taken as pathological. Sometimes organic evidence of a cause is lacking, but usually one or both testes show neoplastic or other abnormal growth, including the production of ovarian tissue. Homosexuality is sometimes brought about by the administration of thyroid or oestrogenic hormone for the treatment of plumage disorders. When it occurs spontaneously, testosterone given by mouth in liquid form, or powdered thyroid gland, can be tried for two to three weeks. Little permanent effect usually results, since pathological changes in the testes, unlike physiological ones, are generally irreversible.

The female genital tract is an asymmetrical structure in almost all species, only the left of the two primitive gonads and ducts persisting. Inherent in this atrophy of the right and hypertrophy of the immature left ovary and oviduct is a tendency to certain metabolic or hormonal diseases, as will be seen later. The ovary of a mature female is at first small and consists of numerous minute cysts or follicles which contain undeveloped ova or egg yolks. Between the follicles is the glandular tissue which produces oestrogenic hormones. At the approach of the breeding season, the glandular part develops and the follicles enlarge one after the other so that there is always one follicle approaching maturity and preparing to shed an ovum or yolk for passage down the oviduct. Some infections, such as salmonellosis, infect the ovary via the bloodstream so that the disease can in some cases pass into the fully developed egg and infect the embryo. This is one cause of dead-in-the-shell and weakly nestlings. In times of stress, excessive cold, food shortage or other forms of bad management, the ovary will not develop to the point of shedding yolks, even in the breeding season. The ovary is sometimes the site of tumours.

The ovum is normally shed directly into the funnel-shaped opening of the oviduct which surrounds part of the ovary. Sometimes, however, the ova fall into the body cavity, from which there is no escape and no possibility of re-entering the oviduct. This may be due to two eggs entering the duct almost simultaneously resulting in one being returned and dropped into the abdominal cavity. At other times, spasm or obstructions of the oviduct may result in a partly formed egg being propelled back up the oviduct and into the body cavity. The displaced yolk or egg acts like a foreign body and irritates the peritoneal lining of the body cavity, eventually causing peritonitis. The egg yolk, made up of a high proportion of protein, is slowly absorbed by the peritoneum. Once in the bloodstream this unaccustomed substance seems to produce a type of allergic reaction as it is now regarded by the body as a foreign protein. This is manifested by outward signs of illness, including depression. An outflow of inflammatory fluid or peritoneal exudate results in the abdominal cavity being filled with discoloured stringy exudate and remains of unabsorbed yolk material. The peritonitis may cause distension of the abdomen and result in respiratory distress. The peritoneal exudate is usually sterile, but if the yolk material becomes infected by bacteria such as Escherichia coli, the bird dies rapidly. The peritoneal fluid may be yellow, cloudy grey, greenish, reddish-brown or black, according to the length of time that the peritonitis has been present. In egg peritonitis gut action may be initially speeded up, causing diarrhoea, but later inactivity on the part of the gut produces little or no faecal droppings. In non-infected cases a bird with peritonitis can live days or even weeks in indifferent health, gradually losing weight, until eventually death occurs. In severe cases of abdominal distension caused by yolk material and exudates, rupture of the abdominal wall may occur. In such cases diagnosis can be difficult unless a small sample of abdominal contents can be obtained by puncturing or opening the abdomen in the midline. It is sometimes possible for a veterinarian to operate, flush and pick out all abnormal fluid and solid material, lubricate the abdominal organs with an antibiotic or saline solution and then suture the abdominal wall. Recurrence, however, may occur. If the bird is valuable and a non-breeder or pet, the oviduct and ovary can be surgically removed. Even in the most skilled veterinary hands the recovery rate is poor. The alternative, however, is euthanasia or a slow death.

Although cage birds are not induced to lay daily like poultry, some species such as budgerigars or zebra finches are encouraged to lay, hatch and rear several clutches in each season, and this can be more than the hen constitution can tolerate. Chilling caused by draughty or damp nesting quarters or poor nutrition may also affect the normal functioning of the oviduct. Spasm or cramp of the organ is one such result. The normal progress of the ovum down the oviduct, which is slow and intermittent, can be checked and even reversed at any stage of development. This may result in excessive amounts of albumen being deposited, and sometimes a double shell may be laid down. Such an abnormally large egg may be passed with difficulty or it may be impossible to pass. On occasion the egg can cause a rupture in the oviduct wall and then pass into the abdominal cavity. Another effect of spasm is for the developing egg to be halted in its passage down the oviduct long enough for water to be extracted from it, thus leaving a hard ball of egg material. Spasms with or without bacterial infection cause inflammation of the oviduct wall and result in thickening and increased production of mucus as well as albumen and calcium salts, thus leading to a total obstruction. In spite of these developments, ripe ova may continue to be produced by the ovary, enter the top of the oviduct and result in further impaction. Atony or paralysis of the oviduct is another closely related condition. When this occurs, a normal fully or partially developed egg may be held up in the oviduct owing to insufficient muscular activity for its expulsion.

Egg-binding is usually attributable to spasm or atony of the oviduct mentioned above. Excessively large, misshapen eggs are other causes, these being commonest at the beginning or the end of a laying period. In species kept in isolation as pets, especially budgerigars, an unmated hen may start to produce eggs, even sometimes late in life, and subsequently develop difficulty in laying which leads to egg-binding. Although the absence of a place suitable to lay may be a contributory factor, the cause of egg-binding in older birds is probably lack of tone in the muscles of the oviduct and abdominal wall rather than muscular spasm. Exhaustion due to over-breeding and out-of-season breeding is an important point in aviary birds. Dietary deficiencies are probably only of importance in so far as they affect general health and condition. Obesity for example, is very important in this connection. Severe deficiencies are much more liable to result in failure to ovulate or failure of the ovum to develop fully into an egg, than to cause egg-binding. Inflammation of the oviduct--salpingitis-is generally accepted as a common cause of egg-binding and associated defects in the process of egg production. Chilling disturbances, especially in the night while roosting, or damp nesting quarters, all tend to cause egg-binding. Although muscular contractions occur, they are not smooth and co-ordinated and a constriction develops in front and behind the egg. This results in straining and exhaustion, and sometimes prolapse of the cloaca or even the lower part of the oviduct. Time honoured remedies consist of holding the bird over a jug of steaming water and anointing the hind quarters with olive oil or liquid paraffin. Although this treatment is claimed to be successful by some breeders, in the author's experience more than half of the birds treated in this way, fail to produce an egg. The handling and further delay merely weakens the bird. Any muscular spasm present is liable to be prolonged or increased by the handling and steam. The sticky oil on the feathers reduces their insulating powers and makes the bird more prone to chilling and infection. Manual manipulation is the only method of treatment likely to be successful.
More information on Eggbinding & My Bird Will Not Stop Laying Eggs can be read here.

Sometimes a cystic distension of the oviduct occurs. This causes general malaise, the inability to lay eggs and a gradual soft enlargement of the abdomen. If the abdominal wall is cut an enlarged oviduct is noticed. The enlargement may occur throughout its length or be only a localised swelling, which is sometimes like a pouch on one side of the duct. The oviduct is usually a creamy colour covered by a few small blood vessels. Occasionally it is grey in colour and the swelling more angular, with clear watery contents containing solid, cheesy masses or particles. Both types probably represent a chronic inflammatory process with outpouring of mucus and abnormal albumen which contains broken-down yolk material. Bacteria are seldom found in this material. Bulges in the oviduct wall probably indicate where an egg or yolk had previously been retained. No medical or surgical treatment can restore normal function to oviducts affected in this way. Clinical signs may be vague. Straining does not necessarily mean that there is some form of obstruction. It is important not to confuse egg-binding and dilated oviducts with other causes of abdominal distension. However, to decide whether the genital or alimentary tracts are affected or if a tumour is present in the abdominal cavity can be very difficult.

Double-yolked eggs may be the result of two simultaneous ovulationís, or the division of one completed ovum in the ovary or oviduct. The frequent laying of double-yolked eggs, however, suggests that there is often irregular passage of an ovum down the oviduct resulting in it being caught up by a succeeding yolk so that the two become enclosed in one membrane and shell. Not all abnormally large eggs are double-yolked. The extra bulk may be due to albumen which was added while a normal yolk was retained for an unusually long period in the area of the oviduct where albumen is laid down. This may happen when there is a mild inflammation present. Extra large yolks are only occasionally found and their significance is uncertain. Small yolkless eggs are sterile. They do not usually cause any trouble and may be considered normal if passed occasionally at the beginning or end of a laying period. If they are produced frequently, they may indicate an inflamed oviduct; aberrant yolks shed into the peritoneal cavity; chronic, infectious condition of the ovary, or in aged birds a fibrous, cancerous or degenerative ovary. Soft or shell-less eggs are most likely to result from calcium deficiency as the result of providing inadequate amounts of soluble grit. Even with adequate grit, however, overbreeding or the end of a normal season may be heralded by one or two unshelled or otherwise defective eggs. If a series of such eggs is passed, inflammatory changes may be suspected, affecting the shell-secreting glands of the oviduct and resulting in inhibited secretion. Conversely, although secretion may be normal, the egg may be passed through the oviduct too quickly for sufficient shell to be deposited. A soft-shelled egg remaining in the lower part of the oviduct does not appear to initiate the normal reflexes and the egg may therefore be deposited anywhere or even retained. Eggs stained by blood and excreta are often of no significance. Excreta on the shell may indicate a mild urinary or alimentary upset or merely a poor state of hygiene in the nest. The contaminated eggs should be gently washed and dabbed dry with absorbent cotton wool. Excessive rubbing to remove stains should be avoided because it damages the pores and may even result in bacteria entering and infecting the egg. The usual cause of blood-stained eggs is a small tear of the cloacal mucosa or rupture of a minute blood vessel, perhaps as the result of passing an abnormally large egg. No treatment is possible and usually only one or two eggs are affected in this way. Broken eggs may occur because the shells are too thin or they may be the result of accidents, such as a fright from a cat or other marauders while the hen is on the nest. Rodents or snakes may be responsible for broken eggs in outdoor aviaries, ground-nesting birds being commonly affected. Soft-shelled or normal eggs laid accidentally on the floor can become a focus of curiosity for other birds, resulting in egg pecking, breakage and eventually egg-eating. It is uncommon for cage birds to eat their own eggs intentionally, but sometimes this may arise and the action becomes a vice. Egg-eaters and careless egg-layers are best isolated lest the bad habits are copied by others. Special attention should be paid to diet. Freedom from boredom is also important. Attempted control of the habit in individuals by using such methods as de-beaking or fitting opaque "spectacles" as used in poultry, are not practicable for cage birds.
More info on problems with eggs such as clear, soft or broken eggs, can be read here

An obvious cause of failure to breed is disinclination to accept the male. Early stages of courtship may be tolerated or even encouraged, but "treading" is strongly resisted. With newly imported or nervous species this may be partly due (as in the cock) to unsatisfactory surroundings and can sometimes be overcome with time and by keeping the birds in a spacious and natural aviary away from disturbance. Hormonal deficiencies or imbalances can also cause loss of libido. Alternatively, neoplasms involving the ovary, especially in budgerigars, can have a similar effect and can also produce homosexual tendencies.

These include various inflammatory conditions of the oviduct, obstructions by degenerate egg material, and torsion or twisting of the oviduct, especially in association with rupture of the abdominal wall. Any illness of sufficient severity will inhibit ovulation, this being more sensitive to such conditions than is the production of sperms in the male.

The interplay of birds pituitary, thyroid, adrenocortical and gonadal hormones is extremely complex and imbalances are common. However, in budgerigars the changes in the colour of the cere do not necessarily reflect gonadal changes, they may merely relate to an altered state of health. Intersexes are rare. These birds are intermediate in appearance between male and female and usually show no sexual interest in other birds. A few show bisexual behaviour patterns, but all are sterile. Anatomically, the gonads may be undeveloped or contain both testicular and ovarian tissue. True complete sex reversal occurs more frequently in the female than in the male. If the functional left ovary is destroyed by disease or surgically removed, the rudimentary right ovary may enlarge, but instead of becoming a normal ovary it develops testicular tissue, so that the hen gradually changes sex. It develops male plumage and in rare cases may even fertilise another hen. Sex reversal in the cock, with a change to female coloration, posture, fat distribution and behaviour is less common. Medical treatment using hormones seldom has any permanent effect.

All about the male & females reproductive parts and how they work or the birds and the bees for birds.


E-Mail: berniehansen@sympatico.ca



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Hamilton & District Budgerigar Society Inc.