present participles and relative clauses

[Jay G.]

1. You guys will hear one of the zoo's most famous birds is singing.
2. You guys will hear one of the zoo's most famous birds singing.
3. You guys will hear one of the zoo's most famous birds will sing.

I really don't know which one is corrent and which one is incorrect.

In the sentence 1, I think "that" is omitted between "will hear" and "one of the zoo's most famous birds" or "one of the zoo's most famous birds" and "is singing".

In the sentence 2, "singing" is a present participle as a object complement. So, this sentence is a right one.

In the sentence 3, I think "that" is omitted between "will hear" and "one of the zoo's most famous birds" or "one of the zoo's most famous birds" and "will sing".

Then in the following sentences, which one is right or wrong and what is the meaning difference?
And which "that" can be omitted?

A. You guys will hear that one of the zoo's most famous birds is singing.
B. You guys will hear one of the zoo's most famous birds that is singing.
C. You guys will hear that one of the zoo's most famous birds will sing.
D. You guys will hear one of the zoo's most famous birds that will sing.

I need your help. I cannot understand their meaning differences and recognize their problems. Please help me.
Thank you.

[Tdol]

1. You guys will hear one of the zoo's most famous birds is singing.
This means that you're about to see the bird and it is singing now
2. You guys will hear one of the zoo's most famous birds singing.
This will be true when you visit, the time of which is not clear from the sentence alone
3. You guys will hear one of the zoo's most famous birds will sing.
This one is a bit dodgy to me- it sounds as if the bird is going to give a concert.