From Betty Rodman:

Re: Tit-for-tat: birds found to repay wartime help (July 6): The only thing surprising about the story concerning the way birds band together for a common purpose is that it is being put forth as something newly discovered. In actuality it’s been around the block a few times. Early animated cartoons always depicted birds banding together sounding the alarm to chase off an enemy. I have seen it in nature many times myself including birds calling each other to some food source. This was always true among songbirds. I think the study is interesting, because I enjoy birds tremendously.