Feather leakage as well as mulberry in the comb can show at any age. An all black feathered bird at six weeks may still turn out to be a cull at five months due to feather leakage, mulberry comb, or other reasons. Culling is an ongoing continuous process throughout the life of the bird. I have a mature rooster that will be "culled" this fall because his legs are shorter than I like. I may have a potential buyer for him already, but if that doesn't work out, he will be put on the market for $1,000.