If you want a Rufflet, either hatch it from a Braviary or catch it on Route 23 (the route right before Victory Road). If you want a Braviary, go to Route 4 and (sorry, I only know it from Pkmn White 2. Sorry all those Pkmn Black 2 users.)
Well start with where Colress cleared the Crustle. Head up up and battle the twins. Continue up then take a right and you will battle a fancy girl. Destroy her and continue. You can battle the ♀Hiker that is moving around if you want to. Go up and you will see a Pokefan. Beat her and look down.
You should see a Braviary. If not, then make sure it's Monday. If you want to get a Vullaby, then hatch from a Mandibuzz. To get an Mandibuzz, I sorry, but you have to trade.