Thank you for the link! The first thing that struck me is that the starling is really in a cage, and Maria has not only chosen to be engaged, but can get out if she wanted. What is stopping her is only her selfish desire for grand position in society. Therefore Maria's quote seems ironic to the reader, and perhaps to Fanny (has Fanny grown to be this critical by now?). I don't know if irony of the analogy can be continued further, but the protagonist in " A Sentimental Journey" genuinely wishes to free the starling and pondering on his own freedom, while Henry Crawford is playing with Maria, inciting her to break the rules just to gratify his own vanity by such demonstration of his power over Maria.