Infertile eggs
I have a pair of cockatiels, the male cockatiel is five years old and the female cockatiel is one year old. Four months ago (when the female was eight months old), they mated and laid four eggs, all of them were infertile . Again, four months later (when the female cockatiel was one year old), repeated mating was done and she laid four eggs, all of which were infertile . Is one of the two birds barren or is there another problem?