Have you ever noticed that some birds hatch with few or no feathers while others hatch with a thick layer of downy feathers? For example, woodpecker chicks are naked when they hatch, while ducklings (baby ducks) are not. You can usually tell a lot about a newly hatched chick based on whether it has feathers!

Scientists say there are two main types of birds: altricial and precocial.

Altricial chicks, like woodpeckers, hummingbirds, and songbirds, hatch with few or no feathers. They’re helpless at birth. Their eyes are closed, and they cannot leave the nest. They depend on their parents to feed them and keep them warm until they grow feathers.

Precocial chicks, like ducks, owls, and chickens, hatch with soft, warm feathers. They can keep their own bodies warm and walk around (and sometimes swim) at a very early age. Some can even feed themselves only a few days after hatching! 

If you read the article at the top of this page, you know penguin chicks have a covering of feathers. But penguins are not precocial because they cannot survive outside the nest at a very young age. Instead, penguins are considered semi-altricial (partly altricial).