Chick.
They are called owlets
The Barn Owl is sometimes called a ghost owl.
A newborn sheep is called a 'lamb'.
A newborn elephant is called a calf.
Harry's owl is called Hedwig, Ron's owl is called Pigwidgeon!
The tiny owl is called the elf owl at 5.25 inches long. The small owl is called the cactus ferruginous pygmy owl at 6 inches long.
A bird that looks like an owl is called a "hawk owl."
A moth that looks like an owl is called an "owl moth."
A young owl is called an owlet or fledgling.
Newborn deers are called "fawns".
the male owl and female owl are both called an owl, but the female owl is sometimes called a hen.
There is not a general term for newborn animals. Different animals are called different things. For example, newborn chickens are called chicks.