Flood Swarms

are the first-ever-seen flying incarnation of the Flood, and were described by developers as "infected buzzards crossed with evil bats". These nasty suckers travel in teeming airborne packs, and can emit barb-like projectiles to puncture enemies. Ensemble Studios have confirmed that Swarms are not the only airborne Flood units - a much larger and deadlier creature remains clouded in secrecy.
 * Flood Swarms