I forgot to say the why of chicks being black. Lavender or "self blue" is caused by an inhibitor of black. It's a recessive gene meaning the bird needs both copies of it to express, if only one copy then it will be black and called a "split". People with lavender birds run splits in pens for several reasons. One is by crossing back to black the color can be enhanced as to not be grey and more blue. Also introduction of genetic diversity is easily done with a black bird as lavender will be harder to obtain and likely closely related to the ones you already have. And lastly one can gain breed type using a black bird. The fancier varieties tend to lack the breed type they are suppose to be. This makes sense as typically another breed is crossed to even make these varieties. By using an excellent type black one can improve their lavender stock.
First cross of lav and black is all black splits. Those splits back to lavender produces 50% lavender and 50% splits (black). If splits are allowed to breed then the offspring is 50% splits, 25% lavender and 25% black. The problem with that is one doesn't know which black carry the lavender gene. It would take crossing back to lavender to find out-if all black chicks resulted then the black parent does not contain Lav gene but all the chicks will be splits. SO it's not a big deal and easily sorted out in generation if splits mate with splits.
Edited by Egghead_Jr - 12/7/15 at 3:47am