If they went via the Yangming range, then following the ridges would take them on an up-and-down path, and the flocks would inevitably become scattered; but if they go via Mt. Kuanyin, which stands by the sea and has a north-south orientation, they can follow the grain of the mountains, expending less effort and keeping the flocks together for safety.
陽明山是東西走向，但候鳥由南北返，若由陽明山走，稜線高高低低，隊伍必定四分五散；若依著靠海、又是南北走向的觀音山，等於順著山勢，較不吃力，隊伍也較集中，減小危機。