>They also did a lot more than follow birds, they relied on keen observation of the ocean (interference patterns in the swells caused by an unseen island), the

>They also did a lot more than follow birds, they relied on keen observation of the ocean (interference patterns in the swells caused by an unseen island), the colour of the clouds (clouds are darker underneath when there is land beneath them) and relied on a sophisticated 'star compass' for latitude navigation. Yes, the National Geographic article / series I mentioned nearby in this thread: https://news.ycombinator.com/item?id=16922701 https://news.ycombinator.com/item?id=16922701 says those sorts of things. So does the Morris West book, IIRC (some of them). In fact, some of the photos in the NG article show a device that may be the same as the "star compass" you mention.