Stephen J. Divers, BVetMed, DZooMed, MRCVS, DACZM, DECZM (herp)
Zoological Medicine, Department of Small Animal Medicine & Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA
Birds are all oviparous (eggs are laid and incubated and young hatch later). Birds may hatch either precocious or altricial but parental care is usually extensive. As a brief review, remember that the mature psittacine hen only has a left ovary and oviduct, while the male has two internal testes. The gonads are located craniomedial to the cranial division of the kidney.
Sexual maturity may occur earlier in birds raised in captivity than it does in their free ranging counterparts. Generally, larger parrots become capable of reproduction at 3-5 years of age. Most psittacines have a defined breeding "season" which is usually early spring to summer. However, they may breed at any time in captivity. Photoperiod appears to be an important factor in reproductive stimulation. Other factors may include presence of a mate, appropriate temperature and humidity, presence of an appropriate nesting area, and nutrition.
Female birds lay down calcium in their long bones, presumably under the influence of estrogen. This calcium is later utilized during egg shell production. Ovulation occurs in response to increasing levels of estrogen and a LH surge. Fertilization takes place in the infundibulum, before the egg passes to the magnum where albumen covers the ova. The egg then moves to the isthmus where the inner and outer shell membranes are acquired added. Finally, in the uterus the shell becomes calcified. This entire process generally takes about 24 hours. Remember that in birds, it is the female that is heterogametic and determines gender of the young. Most parrots lay 2-4 eggs in a clutch, although indeterminate layers, such as budgerigars, lovebirds, and cockatiels can produce larger clutches. After all eggs are laid, there is an increase in progesterone in the hen that inhibits further ovulation and induces physiologic and behavioral changes associated with incubation of the eggs and brood care. Some birds may develop a "brood patch" which is a featherless area over the ventrum that allows closer contact between the warm skin of the parent and the eggs. Prolactin levels also rise and in some species (e.g. doves or pigeons) are responsible for the production of "crop milk" (a nutritive cellular substance formed in the crop that is fed to the chicks).
The following text is brief and only the most common conditions are mentioned. Readers are directed to extensive reviews on the subject for more details.2-4,6
Failure to Reproduce
While generally not a common problem of the pet birds, psittacine breeders will often approach the avian veterinarian for advice concerning non-productive parrots. In such cases, the priority is to confirm the gender of the two paired birds and to evaluate their reproductive tract for anomalies. A standard left lateral coeloscopic examination via the left abdominal airsac is required, and is easily accomplished in the anesthetized bird using a 2.7 mm telescope. Common observations are:
'Proven hens' with an involuted reproductive tract that has never actually produced an egg
Reproductive diseases (e.g. fibrosis/adhesions, gonadal cysts/neoplasia, etc.)
Non-Gender Specific Reproductive Problems
Feather Picking, Self-Mutilation and Other Behavioral Anomalies
Psittacine birds are intelligent animals designed for flight and social/paired existence. Therefore, keeping an individual bird restricted to a small cage that does not permit flight is not only inhumane, but likely to cause behavioral problems. Birds that are bonded to their owners, especially following the attainment of sexual maturity, seem to fair poorly when separated from their owners for prolonged periods (i.e. when owners leave for school or work). Sexual frustration can initially manifest as increased grooming, leading to feather picking, and ultimately self-mutilation. While decreasing owner-bond physical interaction can help in the long term, initially it can often make matters worse. Intra-species aggression has also been reported for various psittacines, but appears most problematic for cockatoos where the male may seriously injure the female.
If the behavioral anomaly is sexual in origin, then leuprolide acetate may be effective, while management changes are instigated. Unfortunately, although orchidectomy and ovariectomy are probably the treatment of choice, they carry significant surgical risks and are often avoided unless the owners have become frustrated with failed treatments and desperate for resolution.
Female Reproductive Diseases
Excessive Egg Production
Excessive egg production is a particularly common complaint of owners of female cockatiels. In most cases, birds are on a high calorific diet (e.g. seed based), kept under long photoperiods, and either interact with a male cockatiel or an overly affectionate owner. Frequent and persistent egg-laying combined with a poor seed-based diet often leads to reductions in body condition and overt health. Certain management changes, like conversion to a pelleted diet, decreasing photoperiod, and reducing 'mate' interactions can be helpful. However, if unsuccessful leuprolide acetate (Lupron Depot, Tap Pharmaceuticals; 800µg/kg IM every 2 weeks for 3 injections), a GNRH analogue, is often effective at reducing reproduction at least in the short term. Some cases will continue to recur and will likely benefit from surgery. Currently it is difficult to recommend ovariectomy due to the risks involved; however, salpingohysterectomy prevents egg laying but not ovulation. Consequently, ovulated ova cause mild focal coelomitis and tend to be reabsorbed. Most low fecund psittacines seem tolerant of the low-level coelomitis associated with infrequent ovulation and ova reabsorption.
Dystocia (Egg Binding)
Dystocia is defined as difficulty in laying an egg, and may be related to a host of factors including lack of nest site, unsuitable environment, poor nutrition, metabolic derangement, and reproductive disease. Most birds present as an emergency, and often with some degree of dyspnea or respiratory distress. Initially, placement in an oxygen incubator, with high humidity should precede detailed examination. Eggs are often palpable but lack of physical detection does not rule out there presence. Once stable, radiographs, hematology and biochemistry (including total and ionized calcium) should establish the diagnosis and bird's general health status. Medical care including fluid therapy, analgesics, and a warm humid environment may encourage laying. In addition the use of topical prostaglandin E1 (Misoprostol) or E2 (Prepidil) and injectable F2α (Lutalyse) appear to be effective for relaxing the uterovaginal sphincter. Oxytocin may also be tried but appears less effective compared to prostaglandins, while parenteral calcium should only be given if hypocalcemia has been confirmed.
If medical treatment fails, then surgical intervention is required. Eggs located within the cloaca or at the uterovaginal sphincter may be removed following brief anesthesia and a small episiotomy incision, or following ovo-centesis. Otherwise, an exploratory celiotomy and salpingotomy (or salpingohysterectomy) should be performed.
Cloacal & Oviductal Prolapse
Prolapse may involve the oviduct, uterus, vagina and cloaca through the vent opening, and may occur secondary to physiologic hyperplasia and egg laying, or dystocia. Excessive straining combined with poor body condition and malnutrition may predispose to prolapsed. Urgent care is required to prevent tissue devitalization. Gentle cleaning, the use of concentrated osmotic preparations and topical antimicrobial/steroid preparations can be helpful to reduce swelling and aid replacement. Stay sutures placed in the cloaca or percutaneous retention sutures are often required for several days.
Salpingitis & Metritis
Salpingitis may occur following airsacculitis, pneumonia, hepatic disease, or retrograde infections of the lower reproductive tract. Various bacteria including E. coli, Mycoplasma gallisepticum, Salmonella spp, and Pasteurella multocida have been isolated. While most common in adults, this can occur in young birds. In medium to large parrots, endoscopic access to the vagina and uterus is possible for the collection of samples for culture, and even irrigation and removal of diseased material. Otherwise, celiotomy may be required.
Oviductal impaction is often seen as a sequela to salpingitis, metritis, or dystocia, and generally involves excess secretion of mucin and albumen associated with cystic hyperplasia, or inspissated egg material within the magnum. Soft shelled or malformed eggs may also impact the distal oviduct. Treatment usually requires surgery and appropriate antimicrobial therapy.
Oophoritis & Cystic Ovary
Abnormal changes to the ovary including infection, inflammatory, degeneration and cystic ovary can be most readily appreciated using endoscopy. Cystic ovary is commonly reported in budgerigars, canaries and pheasants, and may be single or multiple. The precise etiology is unknown but is suspected to be endocrine given concurrent hyperostosis, and oviductal hyperplasia. Cystic changes may progress to neoplasia. Treatment usually involves aspiration of affected follicles combined with either ovariectomy or hormone therapy.
Oviductal Cystic Hyperplasia
Commonly reported in budgerigars and domesticated fowl, the entire oviduct is distended with mucoid to creamy material. Cystic ovaries are also commonly seen. Treatment requires celiotomy to remove the large structure.
Cloacitis, strictures, cloacoliths and chronic cloacal prolapsed can interfere with copulation and egg laying, and may themselves be a result of previous traumatic oviposition. Papillomas or painful conditions of the cloacal may also be evident. Cloacopexy and/or cloacoplasty surgery may be required.
Ectopic Eggs and Non-Septic Coelomitis
Ectopic ovulation may occur naturally, secondary to abnormalities of the oviduct (e.g. discontinuous, ruptured), or as a consequence of previous salpingohysterectomy. If the amount of ectopic material is small then clinical signs may not develop as reabsorption may occur. However, frequent ectopic ovulation leads to accumulation and severe non-septic coelomitis. Surgical removal can be attempted, but material is often adhered to multiple coelomic structures.
Coelomitis is the most frequent cause of death associated with reproductive disorders. Egg yolk in combination with bacterial infection (e.g. E. coli, Yersinia pseudotuberculosis, Staphylococcus spp) appears to be important for the development of disease. Radiology, hematology, coelomocentesis, and endoscopy appear most useful for diagnosis. Most birds are severely compromised and require intensive nursing and supportive measures. Many cases can resolve with aggressive and appropriate antimicrobial and anti-inflammatory therapy alone, but some may require surgical intervention and the removal of inspissated material once stabilized.
Neoplasia may account for up to 5% of reproductive disease. Budgerigars appear to be over-represented with frequent neoplasia of the ovary or oviduct. Large, estrogen-secreting ovarian tumors may result in ovarian cysts, ascites, herniation, hyperostosis, and changes in secondary sex characteristics (cere color changes). Endoscopy or celiotomy and biopsy are required to confirm the diagnosis, and surgical resection is usually very difficult.
Male Reproductive Diseases
Male Cloacal/Phallus Prolapse
Male cockatoos seem particularly prone to excessive masturbation and cloacal prolapses. Phallic prolapses have been reported in ratites and waterfowl. Exposed tissue must be cleaned, carefully debrided if necrotic or infected, reduced in size using hyper osmotics, and gently replaced. Stay or transcutaneous sutures may be required for several days, and is often more effective if combined with leuprolide therapy, and changes in management (e.g. reduced handling of pet cockatoos by owners).
Rarely seen in companion birds, but infection with E. coli, Salmonella spp, and Pasteurella multocida have been reported, usually secondary to prolapsed phallus, renal obstruction, cloacitis, and septicemia. Endoscopic examination and biopsy is usually diagnostic.
Testicular tumors commonly occur in older budgerigars, but can occur in other psittacines. Seminomas, Sertoli and interstitial cell tumors have been documented. Changes in behavior and secondary sexual characteristics may be noted, including a change in cere color from blue to brown in male budgerigars.
Medical & Surgical Therapy
In most cases, birds present in an advanced state of debilitation, and intensive nursing and supportive care is required, often prior to advanced diagnostics. Placement into a warm (85-90oF), oxygenated incubator can help to stabilize the avian patient prior to detail physical examination. Fluid therapy, nutritional support, antimicrobials (based on Gram stains, and culture and sensitivity testing), analgesics and anti-inflammatory medication are key.
The standard approach to the avian reproductive tract is via a left coeliotomy.1 Endoscopic orchidectomy and salpingohysterectomy have also been described.5 These surgeries are complex and not without significant risk. A dedicated anesthetist, along with ventilation, intra-operative fluid support and temperature maintenance appear critical.
1. Bennett, R.A., and G.J. Harrison. 1994. Soft tissue surgery. In: B.W. Ritchie, G.J. Harrison, and L.R. Harrison (eds.). Avian Medicine: Principles and Application, ed. Harrison Bird Diets International Inc, Fort Worth. Pp. 1096-1136.
2. Bowles, H.L. 2002. Reproductive diseases of pet bird species. Vet Clin North Am Exot Anim Pract 5: 489-506.
3. Crosta, L., H. Gerlach, M. Burkle, and L. Timossi. 2003. Physiology, diagnosis, and diseases of the avian reproductive tract. Vet Clin North Am Exot Anim Pract 6: 57-83.
4. Echols, M.S. 2002. Surgery of the Avian Reproductive Tract. Semin Avian Exotic Pet Med 11: 177-195.
5. Hernandez-Divers, S.J., S.J. Stahl, G.H. Wilson, M. McBride, S.M. Hernandez-Divers, T. Cooper, and N. Stedman. 2007. Endoscopic orchidectomy and salpingohysterectomy of pigeons (Columba livia): an avian model for minimally invasive endo surgery. J Avian Med Surg 21: 22-37.
6. Joyner, K.L. 1994. Theriogenology. In: B.W. Ritchie, G.J. Harrison, and L.R. Harrison (eds.). Avian medicine: principles and application, ed. Wingers Publishing, Lake Worth, Florida. Pp. 748-804.