YOU SAID:

I was standing behind the tree, when I saw a bird

INTO JAPANESE

鳥を見たとき、私は、木の後ろに立っていた

BACK INTO ENGLISH

When I saw the bird I was standing behind the tree

INTO JAPANESE

私は木の後ろに立っていた私は、鳥を見たとき

BACK INTO ENGLISH

When I saw I was standing behind a tree, bird

INTO JAPANESE

私は木、鳥の後ろに立っていた私を見たとき

BACK INTO ENGLISH

When I saw I was standing behind the trees, birds

INTO JAPANESE

私は木、鳥の後ろに立っていた私を見たとき

BACK INTO ENGLISH

When I saw I was standing behind the trees, birds