Passerine
All passerine chicks are born in an undeveloped state (altricial): they need parental help. Their eyes are closed, and they are bald, with little or no down. They cannot leave the nest, and must be fed by the parents. The advantage of this is that their brains grow larger during the fledgling stage. In birds which leave the nest early, their brains depend mainly on material in the egg. Passerines have significantly large brains compared to body size, and many passerines are comparatively intelligent.