YOU SAID:

i once saw an old man at the park feeding birds

INTO JAPANESE

公園で鳥に餌をやる老人を見たことがあります

BACK INTO ENGLISH

I've seen an old man feeding birds in the park

INTO JAPANESE

公園で鳥に餌をやる老人を見た

BACK INTO ENGLISH

I saw an old man feeding birds in the park

INTO JAPANESE

公園で老人が鳥に餌をやるのを見た

BACK INTO ENGLISH

I saw an old man feeding a bird in the park

INTO JAPANESE

公園で老人が鳥に餌をやるのを見た

BACK INTO ENGLISH

I saw an old man feeding a bird in the park