Rangmejo

Close-up of a quadwing on Installation 05

Quadwings^[1] are a species of flying creatures that inhabit the artificial ecosystems of a number of Forerunner constructs, namely Installation 03,^[2] Installation 05,^[3] and Installation 00.^[4] They are occasionally hostile, especially in large numbers.^[2]

Despite being of presumably alien nature, these creatures bore a surprising similarity to Pterosaurs, which were an order of reptiles that lived on Earth within the Mesozoic. Their double set of wings and long, rigid tail gave them a striking resemblance to Earth's dragonflies as well.

Trivia

Quadwings appear in the Halo 2 campaign levels Delta Halo and Regret. In Halo 3, they can be found in the multiplayer levels Guardian and Epitaph.
Players can shoot these creatures or stick them with Spike Grenades or Plasma Grenades on several Campaign and Multiplayer levels. If shot, they will burst and fall to bloody tatters in mid-air, their gory ribbons tend to just "poof" in the air with few visible body parts falling. Upon death, the quadwing's body disappears for a fraction of a second, then reappears larger than before.
The birds seen in High Charity in the Halo 2 level Gravemind are sometimes mistaken for quadwings, but upon closer examination, one can see that they are a different species.
In Halo Mash-Up: Minecraft Evolved, the Ender Dragon boss mob is retextured to look like a quadwing.
In response to the increase in questions relating to the quadwing's origins, Frank O'Connor claimed that "They are basically space pigeons, or flying rats. All they do is breed, poop and fly slowly around. Their only known skill is the ability to predict human marksmen and turn just exactly as you were about to shoot them." on an April Fools edition of Halo Waypoint's Canon Fodder blog.^[5]