Chick is the most common usage but is also a slang word to describe a human female. Nestling is a bird that has yet to leave its nest. Fledgling is a bird that is yet to learn to fly.
A nestling is a young bird that has yet to leave its nest, so it may have just hatched or could be fully fledged yet not ready to leave the protection of the nest.
A fledgling is a young bird whose feathers and plummage are in the development stages. A hatchling is a young chick recently broken out of its egg.
"A nestling"とは、まだ巣立つことができない小さい鳥のことです。 "hatched"(孵化した) ばかりか、一人前に羽が生えているが巣の保護から出る準備ができていない鳥のことです。
"A fledgling" とは、羽や羽毛が発達途中の小さい鳥のことです。 "A hatching"は卵からかえったばかりの鳥のことです。
There are different terms to be used for a baby bird, you can just say 'baby bird', a hatching is a bird that has just been born (hatched) from the egg
A Nestling is a baby bird that has not yet left the nest yet
A fledgling is a baby bird that can not fly yet but has left the nest
A chick is any baby bird.
A hatchling is a bird that has just emerged from an egg. It is a very young bird.
A fledgling is a bird that has grown feathers and is about to fly for the first time.
The most common word for a baby bird is a "chick" but you can also call it a "baby bird" or "Nestling.
These are all words to describe a small bird that lives in a nest and cannot yet fly.