Abstract
As we continue to study and learn more about birds from our experiences, we sometimes have a tendency to jump to conclusions from limited data. Let me illustrate.
In early January, a couple from Tampa, Florida, brought in two African Greys for surgical sexual determination. I was particularly interested in African Greys because I had spent some time in the past correlating obvious physical characteristics with the sex, after the sex had been surgically determined.
After carefully looking over the two birds in front of me, I told the owners that I felt confident that they had a pair- one male and one female. One bird was very broad and flat between the eyes and was a more robust bird. This bird also had a large portion of its small red ventral tail feathers evenly diffused with grey color, except the tips, which were dark red. These had proven to be the characteristics of a male in I 00% of those birds examined previously.
The other bird was less bold, was a lighter grey color, had a very sharp forehead and was narrow between the eyes. All ventral tail feathers were white-washed red under natural light, even the very smallest feathers. 57% of the females examined before had fit this description, so I felt this was a female.
Both birds were over 3 years of age and the suspected male was thought to be 7-8 years old.
Much to my surprise, the endoscopic examination of the birds' gonadal tissues revealed them both to be males.
HISTORY
This whole concept started at the Training Seminar on Sexing and Artificial Insemination of Birds held in Houston, Texas, in the spring of 1977.
The zoological world has been working on several methods of sexual determination, and many were presented at that Seminar. One of the most promising methods, hormonal analysis of the droppings, is being done by the San Diego Zoo and is very accurate, but it requires many thousands of dollars of equipment and may not be practical for most breeders for years. Genetic studies are also being done, but require years of normal data to be meaningful.
It was postulated by Robert Berry, the Curator of Birds at the Houston Zoo, that the sex of African Grey Parrots could be determined by the color of the tail feathers. Also, several recent articles have stated that if you observe the feather patterns of mated birds, along with other physical characteristics, such as head width, pelvic bone width, leg stance, etc., you could predict a pair in the future.
Since that time I have studied and photographed samples of tail feathers of all the African Greys that have been brought to the All Animal Clinic for endoscopic examination of gonadal tissue - some 54 birds - and was ready to base a theory on the following data.