I've been observing crows around town for a few years, in part because they seem to be taking over and crowding out other birds, and in part because they're intriguing creatures. They're much smarter than most birds, and clearly adapt well to an urban environment. I was pleased to learn that some of my "observations" had turned out to be accurate. From what I'd seen, for instance, crows spend most of the day foraging alone or with one or two other crows. Then as dusk approaches, they gather in much larger flocks high in the trees. It's not always the same trees, although they do seem to show preferences for areas where there enough trees to accommodate the whole crowd. When they get together in the evening, it looks (and sounds) as if they're each broadcasting all the details of their entire day, all at once and at top volume.
At times, I've seen these gatherings reach into scores of crows. One time last summer, there was a gathering in the trees outside my home and the volume of noise was so great that I had to go outside to look, and discovered at least one of my neighbors had also been drawn to the front door. Incredible. The group, incidentally, is known as a "murder" and reportedly can include crows in their thousands.
Crows apparently have a very tightly-knit family, in which some members serve as "helpers" to breeding pairs. What I've also noticed about them is an enormous number of calls; it's not unusual to observe what sounds like an actual conversation among several of them. According to one of my bird books, they can live as long as 20 years.