Are African grey parrots nocturnal or diurnal?

No, most cockatiels are not nocturnal. Sometimes, however, if you play with your cockatiel more at night, let's say if you work during the day, and you play with your cockatiel at night, your cockatiel may develop sleeping habits to sleep during the day, rather than night, to stay with you, so you and him can play. However, most cockatiels have the same sleeping patterns you do. But-most tiels sleep every bit you can, while you are away, or if they are on your shoulder. They sleep more in their lifetime than they are awake, so your cockatiel will take naps a LOT during the daytime, also.