Long story short, I have a 12 week old and two 25+ week olds. One older bird has no problem with the new comer but the other doesn't want it anywhere with in site. She chases her all over and pecks and grabs her by the back of her neck. She chases her all over the yard relentlessly. I'm new to this, but to me the older birds aggressiveness isn't normal. She, to me, is way too aggressive towards this bird. Is it because she is younger and smaller? Or does my older bird just have a really bad attitude towards new comers?