The crow and the raven have traditionally been regarded as omens of death and ill-fortune
The collective name for a gathering of crows is a "murder".
This term is based on the superstition that crows form tribunals to judge and punish the bad behavior of members of the flock. When a "defendent" was found guilty of a crime and sentenced to death, it was believed, the rest of the flock carried out the punishment - that is, they "murdered" the offending bird.
The superstition is probably based on the fact that crows are extremely protective of their territory and have been known to attack and kill crows that have invaded their space. Crows are also cannabilistic and frequently feed on the carcases of dead crows.
Crows and ravens are also associated with battlefields, execution sites and medieval hospitals because they scavenged on human remains at these locations - and even on the flesh of unconscious soldiers who had been injured in battle.
Many people are unable to distinguish between crows and ravens.
Ravens are about one third larger than crows. They have somewhat heavier bills, more fan-shaped tails, sometimes they have a ruff (mane) of feathers around the throat. But essentially, crows and ravens are identical in colour, shape - and most importantly - behavior.
Throughout history - going back as far as the ancient Greeks - crows and ravens have been regarded as omens of death and evil.
In mythology, crows were also described as possessing mystical powers.
When Apollo discovered that his herd of beautiful white cattle had disappeared, he asked his crows who had stolen them. The crows replied, "It is the twelth god of Olympus, but a day old, who has spirited your herd away."
This infuriated Apollo. "You lying wretches, there is only eleven gods of Olympus. I will punish you for your lies," he said. Then he turned the crows, which had been white as ivory, black as ashes.
According to another legend, crows were as white as swans until one day a raven told Apollo that Coronis, a Thessalian nymph whom he passionately loved, was faithless. The god shot the nymph with his dart; but, hating the tell-tale bird:
He blacked the raven o'er
And bid him prate in his white plumes no more.
Jovianus Pontanus relates two skirmishes between ravens and kites near Beneventum, which prognosticated a great battle. Nicetas speaks of a skirmish between crows and ravens as presaging the irruption of the Scythians into Thrace. He also relates that his friend Mr. Draper, "in the flower of his age and robust health", knew he was at the point of death because two ravens flew into his chamber. Cicero was forewarned of his death by the fluttering of ravens, and Macaulay relates the legend that a raven entered the chamber of the great orator the very day of his murder, and pulled the clothes off his bed.
Because crows and ravens are so long-lived, the Greeks associated them with time and memory, and with their "father time", Cronos. The two ravens that sit on the shoulders of Odin are called Hugin and Munnin (Mind and Memory), and in fact the roots of the words for "time" and "crow" are intimately associated.
Studies have revealed that ravens and crows are highly intelligent - more intelligent than chimpanzees, and possibly as intelligent as dolphins. They have often been observed playing with dogs as a human might, and are capable of amazing auditory reproduction simulating all manner of sounds from their environment - including human speech.