The feed is gravity fed into a smaller holding container. A spring(auger) moves this feed down the indicated pipe(about 25mm diam), through the feeders(containers the birds feed from). The feed falls through holes in the pipe in which the spring is turning and moving the food as a result. Usually 2 feeders at a time will fill up to the hole in the pipe. The feed them effectively blocks the feed from falling from the pipe, and causes the next two feeders to start filling up etc, until we reach the last. When the last one reaches a certain level, it must stop the motor, and then restart when a minimum level is reached.
Hope this makes more sense.