Does anyone know the bird and cage tradition after sharing a bottle of champagne?

Answer 1

Yes, as far as I have heard it is a French tradition known as, "des oiseaux et cages." It goes in that whomever opens a bottle of champagne gives the other drinker an option to take the wire cage or the cork (the bird). You then must agree to hold onto either object until you see each other again (this is usually done between two people who don't see each other often). If upon seeing each other again one person can produce their object and the other cannot, then the one without their piece must buy the next bottle of champagne.