I saw this in action. Parking under a tree with some sort of cherry every day, I saw the day the flock arrived. It was about 1 or 2 days before the fruit ripened. The flock's members proceeded to pluck each fruit from the tree, test it with their beak, and 9 times out of 10 drop it on the ground as too green. Stripped the tree in a minute.<p>If the flock had waited a day, of course, each bird would have had 10X the fruit. But any member of the flock that waited that day would have found a stripped tree. Hard to see how the genetics of the bird flock could ever escape this tragedy.