Am I correct about possessives?

Question

1 When you say about a bird in general, you say "This is a feather of a bird", you can also say "This is a bird's feather".

a. So when you say "These are feathers of a bird", so will you say "These are bird's feathers" or "These are a bird's feathers"?

b. You will not say "This is a cage of birds / This is a birds' cage", because there is not a cage belong to all birds in the world, right?

2 When you say about a bird in particular (the bird you bought yesterday), you say "This is the cage of the bird", you can also say "This is the bird's cage".

a. So when you say "These are the cages of the bird" (several cages for one bird), will you say "These are bird's cages"?

b. So when you say "This is the cage of the birds (the birds you bought yesterday / one cage of those birds)", so would you say "This is the birds' cage"?

3. When you say about a man in general, you say "This is a wallet of a man" / "This is a man's wallet", you can also say "These are wallets of men. / These are men's wallets.".

But you will not say "This is a wallet of men. / This is a men's wallet." because there is not a wallet belong to all men in the world, right?

4. But when you say about a men in particular (the man you told to me yesterday):

a. You can say "These are the wallets of the man." / These are the man's wallets.", right?

b. And if those are some men, you can say "This is a wallet of the men." / "This is a men's wallets.", right?

Thanks!

Answer 1

1a) These are a bird's feathers.

1b) This a complex one because there is a noun "birdcage" that means a cage for one or more birds. But you can say "this is a bird's cage" without necessarily implying that it cannot hold more than one bird.

2) Actually the more common phrasing would be "This is the bird's cage." The prepositional phrase indicating possession is less common than using the possessive case.

2a) You would say "These are the bird's cages" because we are talking about a specific bird.

2b) It is certainly correct to say "This is the birds' cage." However, this might be the case where a native speaker who was being careful to avoid ambiguity might say "This is the cage of the birds" because in speech there is no difference in sound between "bird's" and "birds'."

3) You essentially have it. The only caveat is that plural forms do not necessarily imply all.

4a) You have it.

4b) This is a strange hypothetical because it is unusual in the extreme for more than one man to share a wallet. But if the situation arose, you would say "This is the men's wallet." The article is determined by the possessor, not the possession.