Why do I have to send blood to sex some species?

The DNA extracted from the feathers is obtained mainly from a small clot of dried blood that is located in the barrel of the feather. This clot is a relict left over from the formation of the feather. Although this process is similar in all birds, the amount of blood that makes up this clot differs not only between species but also between feathers of the same individual. Because of our experience in the laboratory, we have identified those species in which the amount of DNA extracted from their feathers is not enough to perform the molecular sexing. For this reason, we ask our customers to send us blood instead of feathers for a small number of species.