Sex determination in birds
Did you know that birds have a ZW system for determining sex instead of the XY system that we humans have? In birds ZZ is a male and WZ is a female. This makes the female the heterogametic sex instead of the male. When I read about this my first response was to ask does that mean that a bird can survive if it just has one Z? What would that bird be like? To my dismay however a bird cannot survive with just one Z and we don’t know what it would be like because it dies too early. This is because in birds one chromosomes doesn’t inactivate like what happens in humans instead both doses are needed. My next question is can a ZZW bird exist then? The answer to this is yes but they are extremely rare and we don't have enough information on them yet to determine if it is the Z or the W chromosome that takes a more dominate role in deciding male and female. If you want more information This site talks about one of the three Charadrius alexandrines that have been recorded.
On I related note I read Mile's blog and was very interested in Gynandromorphy so I looked up more information about it and found this article. They were experimenting on birds and one of the experiments that they did was they took cells from very early in development and moved them into a environment that was overwhelmingly of the opposite sex and tested to see if these cells would conform with their surroundings. They did not and it was concluded that the sex of the cell was determined at sperm entry.