My previous cockatiel was a hen and she would occasionally lay eggs which were, of course, infertile since I had no male. I saved some of those eggs as amemory of her. A day or so ago I found some in a dish on the back of my dresser. I was curious to see if Bennie would show any recognition of eggs of his own species. (Both birds of a pair incubate, right?) Well, I held them in the palm of my hand and showed them to him. He hissed and backed up as if to say, "No way! Don't look at me; I'm not the father!"