Plural Possessive Nouns

A plural possessive noun shows more than one person or thing owning something.
The singular noun does not end in s, to show possession you must add an apostrophe and s ('s). EXAMPLE: one bird's nest
To form plural possessives you must first change the noun to a plural by adding an s, and then add the sign of possession with a apostrophe AFTER the s (s'). EXAMPLE: two birds' nests