YOU SAID:

that bird's tweets are mine

INTO JAPANESE

その鳥のさえずりは私のもの

BACK INTO ENGLISH

The birds are mine.

INTO JAPANESE

鳥は私のものです。

BACK INTO ENGLISH

Bird is mine.

INTO JAPANESE

私の鳥です。

BACK INTO ENGLISH

This is my bird.

INTO JAPANESE

これは私の鳥です。

BACK INTO ENGLISH

This is my bird.