when I was a kid, it was known that birds knew where they were migrating to, and could find places over and over, and maybe there was some sort of organ or faculty that could sense the earth's magnetic field. Well, science marches on: it is now apparently known that robins, at least, can literally see magnetic field lines overlaid on the vision in their right eye (only!). How cool is that?

https://www.discovermagazine.com/robins-can-literally-see-magnetic-fields-but-only-if-their-vision-is-sharp-8468