DNA bird sexing is useful for many bird species where sex of the animal cannot be determined by physical characteristics (size, colour, etc.). DNA for the test can be obtained from feathers, blood or eggshell. DNA test is a very reliable and is not painful for the animal. Owner of the bird should carefully label samples as false labelling is the most common cause for mistakes.
Bird sexing with genetic methods is based on the fact that there are genome differences between males and females. Like in humans sex difference in birds is based on sex chromosomes. In birds two different sex chromosomes (WZ) are present in females and two same chromosomes are present in males (ZZ). Length differences of certain stretches of DNA on sex chromosomes evolved through history due to the fact, that sex chromosomes do not exchange genetic material like other chromosomes. Length differences are detected by genetic methods and tell us which two sex chromosomes are present in tested individual (WZ or ZZ).