I have two cockatiel chicks,ages fifteen days and the other twenty days. Both are doing very well and maturing every day. However i'm curious as to why the oldest chick has no signs of a crest. (And by the way,the father had to be removed from the cage for preening the chick to hard) but the rest of the body is feathering in nicely even the younger sibling,at fifteen days,is growing a crest...how can this be? Are there such things as "crestless" cockatiels?? Did the father maybe pull them out when he saw them starting to come in?? The crestless chick WAS about the same age,twelve to fifteen days,when the father had to be removed to another cage.. Thankyou for responding..