Because I have received so many calls and e-mails on the subject of inbreeding I thought I should just write something. Most people don't seen to understand just how dangerous inbreeding can be for the chicks or the future gene pool of the species. When it comes to this subject I believe ignorance is no excuse. Common sense should tell you that inbreeding isn't wise. It's not heathy for people, why have your finches do it?
I know how easy it is to let finches inbreed, especially if they are housed in communal flight cages. Even I've had accidental inbreeding happen. What was the result of the Father/Daughter mating? One chick died a day after hatching. The second lived to fledgling but had no eyes (empty sockets). It died as result of a neurological defect. The third one lived to fledgling but had no feet and died as result of an under developed digestive track. That's right 100% fatality.
Parent / Child & Sibling pairings are always a big mistake unless you know the genetic history of your birds for at least the last 3 generations and even then it's a risky gamble with the health of the offspring. When inbreeding is used to produce better color, conformation, or size in a show bird it's often done by an experienced breeder using a pair of cousins. This gives you a slightly more reliable gene pool to work with. Of course, inbreeding isn't something you should attempt unless you are an experienced breeder and understand the genetics of what you are trying to produce.
As some of you may know, it's not possible to import some exotic species of finches from their native countries anymore. This is just another reason why we need to keep the birds we have as genetically healthy and diverse as possible.