Hi there, i've got two pairs of cockatiels.The eldest pair are about 4yrs.and the other are about 1 1/2.The older female has stopped laying eggs,the last time was 6mths ago and were infertile as were the last 3 clutches before that.she never used to have any problems as the younger female is the daughter.They still mate alot and feed each other.The younger pair are ok as they are sitting on 3 eggs just now.If anyone can give any advice it would be great.Thanks.

Gordon..