BIRD SEXING METHODS which should YOU choose?

Abstract

Zoos and private aviculturists have long been faced with the problem of sex identification in psittacines or parrottype birds. Slight differences in color or feather pattern, as noted in cockatiels, 1 do not apply for sexing many species which lack sexually distinct physical or behavioral characteristics. Several scientific techniques have been developed within the last 5 to IO years for reliably sexing these monomorphic birds: 1) surgical sexing, 2) hormonal sexing, and 3) genetic sexing. This article is intended to compare these three documented methods to describe the pros and cons of each and to provide you with the necessary 'information to choose which is preferable for you.

I. Surgical Sexing Methods

A. Historical Comments and Procedures

Direct visual examination of internal avian gonads (male testes or female ovary) is an old and proven sexing method. It is applicable to many types of birds, even when performed under field conditions or as a house call service. The gonads can be seen with the naked eye through a small incision (10-15 mm) made through the skin and abdomanal wall of the bird's left side near the last rib.2 New and more sophisticated equipment has improved viewing of the gonads through a smaller incision. The oroscope> (also used for ear, nose and throat exams) and the laparoscope4 (a fiberoptic telescope) are currently preferred. The basic surgical approach is still on the bird's left side near the last rib with minor variation. Safer injectable anesthetic drugs are available, but the need for general anesthesia during surgical sexing is a debatable issue. Many veterinarians prefer only to restrain the bird, thus eliminating the risks of anesthetic complications. Either procedure is well-tolerated by many types of birds and complications are relatively infrequent. However, with any surgical procedure complications can result in an unexpected death of a bird. Your best assurance for safety is a healthy bird and an experienced avian clinician. The cost of surgical sexing ranges from $15 to $ 7 5 per bird as determined by the individual pracuuoner. Some even offer house call service.

B. Advantages

The major advantages (see chart for comparisons) are immediate results without delay for lab analysis and the potential for sexing immarure and I or inactive birds. A physical exam of the bird is also recommended and should accompany surgery. Reproductive condition may be approximated by comparing the relative size of a bird's gonads. This is very dramatic when looking at the ovary of a hen just before laying occurs. Physical abnormalities of the bird's reproductive tract may also be identified, as well as several disease problems with other internal organs.

C. Disadvantages

The major disadvantages (see chart) concerns trauma and stress from handling the bird, also the risks of surgical complications and ultimately the death of a bird. Mortality rates are variable (l-10%+) and unpredictable. An experienced avian clinician should be sought although one may not be available in your area. Obese birds, diseased birds or those with immature and undeveloped gonads may not be surgically sexable. The long-term effects of surgical sexing upon future reproduction are not fully known; detrimental effects have not yet been documented.

II. Hormonal Sexing Method

A. Historical Comments and Procedures

Avian gonads have two major functions: 1) to produce gametes (eggs or sperm), and 2) to produce hormones (sex steroids) which act throughout the body like messengers to stimulate and regulate sexually related growth and behaviors necessary for reproduction. Gonadal functions in humans and domesticated animals have been studied for many years by measuring the level of hormones in blood or tissues or less frequently in the animal's urine. Blood or tissue samples were not easily collected from exotic birds and separate urine collection is not possible in birds. Therefore, research began at the San Diego Zoo to investigate a non-invasive fecal steroid analysis method which measured the level of metabolized hormones in the mixed feces and urate droppings of birds. 5 Total excretory estrogens (E) and testosterone (T) hormones were measured and evaluated as an E/T ratio. Both types of hormones are produced by the gonads of each sex, but in different proportions. Functionally, mature female parrots produce more E than T and are indicated by a high E/T ratio (greater than 2. 0). Sexually mature male parrots produce more T than E and are indicated by a low E/T ratio (less than 0.6). Immature or sexually inactive birds are frequently indicated by an E/T ratio approaching 1.06 Due to low daily hormone levels produced by inactive birds, they may not be consistently sexable by current hormone methods. Validation of hormonal sexing has involved extensive comparison of E/T ratio data from a wide variety of known-sex birds to determine the range of acceptable values for unsexed males and females, based on the specific analytic techniques described....