Easy english question, 10 easy points?

If you read Zunden's reply carefully, the explanation is basically there. The old lady was in the park - she walked through the gates and then she was inside, and there was a fence or a wall.The birds, however, were less restricted: they could fly in and out, up and down, over or through the gates and fence, perfectly freely; I see no problem with saying The birds were AT the park. They were not inside in the restricted way that a human being has to be.