At the start of your Pokemon Brilliant Diamond & Shining Pearl campaign, you'll notice there aren't many Flying-type Pokemon to choose from. You're likely to run into countless Starly, but exploring dark caverns will net you the Poison/Flying-type Zubat. Although weak, this Pokemon evolves into Golbat and Crobat, ideal Pokemon if you need a speedy attacker. In Brilliant Diamond/Shining Pearl, there are several ways of obtaining Zubat and Golbat. If you want Crobat by the time you face the Elite Four, then you'll want to get the Bat Pokemon as soon as possible.