YOU SAID:
A man went to buy a bird but they were out, so he gave them the bird.
INTO JAPANESE
男が鳥を買いに行ったが、彼らは外に出ていたので、彼は彼らに鳥を与えた。
BACK INTO ENGLISH
The man went to buy birds, but they were out, so he gave them birds.
INTO JAPANESE
男は鳥を買いに行ったが、外に出ていたので鳥をあげた。
BACK INTO ENGLISH
The man went to buy a bird, but he gave it because he was out.
INTO JAPANESE
男は鳥を買いに行ったが、外出していたのでそれをあげた。
BACK INTO ENGLISH
The man went to buy a bird, but he gave it because he was out.
That didn't even make that much sense in English.