Baby names for animals are especially used for those that have been in domestic use for ages already.
The less an animal is for domestic use, the less supposable is a name for its baby animal, though older names that have been in existance already were taken for other animals, too.
A chick is the name for any sort of baby bird. A hatchling is a very new, recently hatched baby bird. A nestling is a bird that has not left the nest yet. A fledgling is a bird the has already left the nest, but isn't yet weaned an eagle is an eaglet. chicken = chick goose = gosling pigeon = squab