Breakdown of У него есть птичье перо.
он
he / it (for a masculine noun) / it (for a neuter noun)
у
at, by
есть
is, there is, to have
перо
quill / feather
Questions & Answers about У него есть птичье перо.
Why does the adjective птичье end in -ье instead of a standard neuter ending like -ое or -ее?
Because it belongs to a special group of possessive adjectives (often made from animals) that end in -ий in the dictionary form. When describing a neuter noun like перо in the nominative case, the ending is -ье. The soft sign (ь) is the defining feature of how these words decline.
Will the soft sign (ь) in птичье disappear if the word changes case?
No, the soft sign actually stays in almost all forms! For possessive adjectives like птичий, the ь remains everywhere except the masculine nominative (and inanimate accusative). For example, if you needed the genitive case, it would be птичьего пера.
Could I use the genitive case of the noun and say перо птицы instead of using птичье?
Yes, перо птицы (feather of a bird) is completely correct and carries the same meaning. However, using animal possessive adjectives like птичье or медвежье (bear's) is extremely common and natural in Russian for body parts, tracks, or products of an animal.
As a quick refresher, why are птичье перо in the nominative case here, even though they are the objects he has?
In the Russian possession structure У него есть (He has), the item possessed is the grammatical subject of the sentence. It literally translates to "By him exists a bird's feather." Since the feather is the subject doing the "existing," it takes the nominative case.