A group of ravens is called a ‘murder’.
This may be because the Norse god Odin, like Zeus in Greek mythology, took on the form of a raven or because they would often eat carrion and act as scavengers. It might also have something to do with their raucous cawing.
Biologists, citing information from Jerry Lemenuik’s book Michigan’s Crow Country, claim that when traveling in search for food in an unfamiliar territory they rely on one bird for directions until it spots familiar landmark (such as an old nest) where they go to roost at night and next day birds come out one by one.