Stingray

Avian Stingrays (the name was never revealed in the episode but UNIT refers to them as that) are a species of swarming aliens that open wormholes using their velocity and numbers (swarms exheed 1,000,000,000 individuals) to open wormholes. They then fly through the wormhole, move onto the next planet, destroy all life, turning it into a barren wasteland and making another wormhole. This process was ended when The Doctor and Malcolm closed the wormhole, trapping them on San Helios. It is unknown what happened to them then, but the most likely explanation is that they starved.

They can fly though the wormhole without a protective vehicle because of their metal exoskeletons. This protects the swarms so that they can fly into wormholes without having their skin and tissue burned off.