Terri Luthe voted up Anonymous' answer 11/20/2015 How Do I Tell If My Cockatiels Are Pregnant? Are asking about Cockatiels parrots? If yes then they belong to class aves and lay eggs not give birth. They lay eggs once in two days. Their clutch contains 4-5 eggs. Incubation period is 18-22 days. For more details, visit Cockatiels.