The ancients may have felt that "If only Du Yu were not in the mountains, roaming among the scenery we would forget to go home"; but bird lovers today all over the world would surely want to change this to: "If only Du Yu is in the mountains, roaming among the scenery we will forget to go home."
古人「若使山中無杜宇，登山臨水定忘歸」，對今天世界各地的賞鳥族，恐怕得修改成「若使山中有杜宇，登山臨水定忘歸」了。