I've seen this behavior with ruffed and blues. Never payed attention for a mama san, but groups of ruffed/blues 3 or more we have always seen 1 lookout when we can spot it. We shoot the lookout first, and easy pickings on the rest typically. If you shoot the feeder first, lookout flies and rest follow. Their are always exceptions I'm sure, but like I said for groups of 3 or more seems to apply. Its not hard to shoot grouse, but it always helps to work on your powers of observation before pulling the trigger.