Ravens are one of several larger-bodied members of the genus Corvus, identifiable by their black plumage and large beaks.
A notable breed is the Northern Raven. They frequently fed on garbage, which ensured they survived even in places like Alaska. In addition, they also have long lifespans, reaching close to 70 years for Northern Ravens, and was the reason behind the wives-tale of ravens having three times the lifespan of humans, who likewise have three times the lifespan of crows.
Several ravens inhabited the United States Naval Prison Facility in Cuba in the 1970s, as well as both Northern Kabul, Afghanistan and the Angola-Zaire Border Region of Central Africa during the 1980s, with Diamond Dogs rescuing a few. Ravens, or at least crows, also were a major threat during the second parasite outbreak at Mother Base in 1984, as they were circling the quarantine platform to feed on the soldiers that were infected with parasites and spread it to land. Many of them were destroyed with napalm fired at the outside just as some parasite-infected soldiers made it outside.
During the Shadow Moses Incident in 2005, the population of Northern Ravens boomed after FOXHOUND arrived and took over the facility on Shadow Moses Island. Several ravens roosted in the freight elevator shaft and warehouse of the underground maintenance base, and several aided Vulcan Raven in fighting Solid Snake. After Vulcan Raven was defeated and mortally wounded, his ravens ate him alive, leaving literally nothing behind afterwards. Northern Ravens were were still present during Snake's return trip to Shadow Moses in 2014.
Behind the scenes
In Metal Gear Solid, ravens are encountered prior the the boss battle with Vulcan Raven. Should the player kill any of the birds beforehand, Raven will express anger towards Snake when they meet in the warehouse.
Killing the ravens in Metal Gear Solid V: Ground Zeroes serves as one of the trials for the game. If the player runs into them while using the speed boost of either Raiden or the Cyborg Ninja skin, they will proceed to explode into feathers.