A Passenger Pigeon
The passenger pigeon or wild pigeon (Ectopistes migratorius) is an extinct species of pigeon that was endemic to North America. Its common name is derived from the French word passager, meaning "passing by", due to the migratory habits of the species. The scientific name also refers to its migratory characteristics. The morphologically similar mourning dove (Zenaida macroura) was long thought to be its closest relative, and the two were at times confused, but genetic analysis has shown that the genus Patagioenas is more closely related to it than the Zenaida doves.
Passenger pigeons do not spawn naturally. They can be revived if the player brushes up a Passenger Feather from suspicious sand. When the feather is found, it can be placed in a DNA extractor, which can form it's spawn egg. Bringing the passenger pigeon back to life will give you the achievement "Martha", as the last Passenger Pigeon's name was Martha.