They're called down
Young ducks are called ducklings. They are typically born with soft, fluffy feathers and are often seen following their mother closely as they learn to swim and forage for food.
No baby birds are born with fine feathers called down that makes them look fluffy and almost furry. When they grow up they develop regular feathers and look like chickens.
LOL. Ok, so yes, in a way penguins are fluffy, but only when they are young. By the time they grow their adult feathers they are sleek and waterproof.
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. These fluffy feathers are designed to insulate birds to keep them warm.
owlet feathers
It's called a fledgling this means that a bird had just grown its feathers
A pumage refers to the soft, downy feathers found on birds, particularly in young or juvenile birds. It provides insulation and warmth before they develop their adult plumage. In a broader sense, the term can also describe the overall feathering or appearance of a bird. However, it is most commonly associated with the fluffy, softer feathers that help in thermoregulation.
When a penguin is a chick, it has gray down feathers. As it gets older and more mature, the down is replaced by the smooth, water-proof, back and white feathers you are used to seeing.
fluffy puppy, Fluffy Scruffy
A young duck is called a duckling.
Fluffy Puppy, Fluffy Scruffy
A young sparrow is called a nestling. Nestlings are born without feathers and are dependent on their parents for food and care until they are able to fend for themselves.