Birds are not naturally featherless. If you see a featherless bird, either it is a genetic disorder, has been genetically altered, or simply has been plucked very recently.

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It depends what you mean. Do you mean partiually or fully?

Partially featherless isn't uncommon in captivity, and fully featherless has been heard of. But these are rare mutations, like Yoda the cat with 4 ears.

no , ostrich have feathers

eating bird

Yes. Researchers observed featherless black-footed (AKA African) penguin chicks at a rehabilitation center in Cape Town, South Africa