I live in Palm Springs, California. The vegetation is largely palm trees, and there is a group of about 20 crows that settle into those trees toward dusk, and have been doing so all Spring even to the present day, Mid-July. They call back and forth for a couple of hours. There are also several ravens in this neighborhood, sometimes in clusters of 4 or 5. Not sure who it is, but either the crows or ravens harass a pair of kestrels that have settled into one of the palms. Only once did I see a very large congregation of crows: about 60 gathered on the roof of a house directly across the street from ours and carried on for about an hour before dispersing.