A gathering of crows is called a murder. A murder of crows. True story.
A murder of crows. Because the sites of murders are popular gathering places for crows. A dead fox will draw a few crows, but a good murder, well… a good murder will draw a good murder of them.
Two enemies meet at a crossroads and fight; one kills the other and flees, leaving the body. The crows come to feed; the murder gathers to finish the work of the murderer.
Next week there will be another murder, at a different crossroads on the other side of town. The crows will shift their operations over to the new location. Crows are the ultimate migrant workers.