I recently lost two of four chicks that were my first bator hatch. My fault, apparently I put them in with the hens too soon. The Roo had no problem with them but apparently their mothers did. The two black Orps that laid the eggs were the aggressors. Luckily my favorite survived by hiding in a nesting box until I could come to the rescue. She is a Black Orp / White Silkie cross. She is all black with feathers on her legs and a tuft on her head. It will be interesting to see how she feathers out when she is older. Is there a standard length of time or age that one can begin considering introducing the new birds to the flock?