Where do you use an apostrophe when say birds?

An apostrophe is used with the word "birds" to indicate ownership or possession. For example:

* The bird's nest is in the tree.

* The birds' feathers are beautiful.

In the first example, the apostrophe indicates that the nest belongs to the bird. In the second example, the apostrophe indicates that the feathers belong to the birds.

Apostrophes can also be used with "birds" to indicate a contraction. For example:

* The birds'll be back in the spring.

* The bird's eating a worm.

In the first example, the apostrophe indicates that the word "will" has been contracted to "'ll." In the second example, the apostrophe indicates that the word "is" has been contracted to "'s."