From Halopedia, the Halo wiki
Moa are large flightless bird-like creatures that were native to Reach. They are found on several Human colonies due to exportation, however are close to extinction on their native homeworld.
Moa are large flightless bird-like creatures that resemble extinct Earth-based Moa. The average Moa has two legs and two wings, with their body being covered with features, with scales from the neck up leading up to a very lizard-like head. The Moa have a yellow colored eye which can be closed with an eyelid. Some Moa feature a purple head crest on their heads.
Moa were indigenous to the planet Reach prior to its fall in the summer of 2552. The species was known to live in the Viery Territory, being present in Visegrád, and in the Eposz continent at Szurdok Ridge. Following the Fall of Reach in the summer of 2552, the Covenant's attack on the planet brought the Moa's numbers to near-extinction levels. However, Moa still survive on Reach in remote sectors of the planet that were not glassed by the Covenant.
Moa have also been exported to other Human colonies and locations such as Earth and Casbah. The largest single population of moa is located on the Inner Colony of Gannick 22. Wiljax Brantley, entrepreneur and owner of the restaurant and petting zoo Have S'Moa, had a population of moa shipped to the planet from Reach just before the attack.
Use by Humans
Moa are widely exported to human worlds to be kept as pets.
Prior to its fall, the moa were consumed by humans on Reach. The New Alexandria fast food restaurant chain World Cuisine had advertisements promoting moa burgers, priced at 7.77cR. "Moa Wings" were also sold out of vending machines.
Moa are frequently exported to other Human worlds as food. The zoo Have S'Moa sell various Moa consumables such as Moa burgers, and Moa nuggets which are have now become an incredibly expensive delicacy among wealthy Unified Earth Government dignitaries.
The Moa appear as ambient life in Halo: Reach. The Moa are harmless and will not attack the player. They will take shelter under bridges and other formations when there is a battle nearby. Neither human nor Covenant AI are hostile towards the Moa, although if the player kills one while near friendly AI, such as a member of Noble Team or Army Troopers they will sometimes comment as if an enemy had been killed, and maybe fire on the Moas corpse.This is most likely a small oversight, as Bungie programmed NPCs to fire on dead enemies the player killed. Moa appear as white dots on the player's motion tracker, and the player's reticle does not change color when it is pointed at a Moa. However, if the player melees a Moa at close range, it is possible to lunge towards it, as if they were an enemy. Moa are also affected by the Mythic Skull doubling their health.
The first time that Moa are encountered in Halo: Reach is when several bolt around a corner in an early part of the campaign level Winter Contingency before contact with the Covenant, causing many players to shoot and kill the birds by accident. They are once again and lastly seen in Nightfall, shortly after fighting the two Gúta.
List of appearances