I had 2 cockatiels then found a 3rd on the street. It was obviously hand fed since it came to me when I found it. After isolation and looking for its owners, we put the new bird in with our 2. Our 2 started mating and we put in a nest box so they could lay a clutch of eggs. We thought the new bird was a male because it liked to hang out with our female, but now we think it’s a female because she wants to go in the nest box, and actually laid an egg in there. Our original 2 had a clutch of 5 eggs and 1 hatched this morning. Now there are still 5 eggs with the baby chick. I think the new bird laid an egg in the nest box. She actually sits in the nest box sometimes (next to the bird that’s sitting on the eggs). So far she hasn’t harmed anything. The male doesn’t seem to like the situation, but the female doesn’t mind another bird being in the nest box.
Should I get another nest box for the new female? I don’t think she mated with the male (at least not that I’ve seen).