Yes! It follows the common rules for breeding. Two long feathered birds bred together will most likely produce a few offspring with shorter feathers than themselves, many offspring with the same feather length, and a few offspring with longer feathers. This is because it is a quantitive trait. Many genes have tiny effects on birds, making the feathers just a little longer, the comb just a little bigger etc. The more homozygous genes you have for long feathers, the longer the feathers are. There is a limit to expression. Expression is limited by the number of these genes. When they are all expressed, you can't get longer feathers unless a new gene mutates, which probably isn't going to happen.
You will most likely get positive long feathered results by breeding within a breed rather than crossbreeding. That is because inbreeding brings homozygous results.
