In Gascony, quince trees are traditionally planted as boundary markers. The quince was once highly regarded in the United States for preserve-making because of its high pectin content, and for the sweet-tart flavor it imparts to stews, but it is not so prevalent today. These days, you are most likely to find it in specialty markets. It is rather unsightly, with hard flesh that is impossible to eat raw. Prepare quince purée and sauce at least 1 hour before you cook the duck.
Wine recommendation: A burly, tannic Madiran wine, of course, like the 1997 Château Montus. This is a really big wine that holds up well to the rich taste of the magret. Another good choice is Domaine Capmartin.