I’ve been reading a newly published book, “Wayfinding - the science and mystery of how humans navigate the world”, by M. R. O’Connor.
There is much written about trying to understand how and why the hippocampus part of the brain controls both memory, and understanding spatial relationships, the locations of places in the world, in both humans and animals.
The 5th chapter, Birds, Bees, Wolves, and Whales, is the mystery of how various creature that migrate seasonally to places thousands of miles away. How do whales travel from the southern oceans to the northern oceans and follow the same route within 1˚ of accuracy despite storms, and ocean currents.
The Bar-tailed Godwit birds migrate from coastal Alaska and fly for 8 days over open ocean to New Zealand. A small error in navigation direction or distance would be the end of them. How do they do it?
Many creatures need; an annual clock, lunar clock, tidal clock, sidereal clock, and a circadian clock, to do the things they do. Some seem to navigate by the sun, moon or magnetic field. But no organ that senses magnetic fields has been found. Perhaps its sensed by a mineral in a cell or cells, such as magnetite or cryptochrome that provides them a quantum bio-compass.
Others if their view of the moon, sun or stars is blocked and they can only see the blank sky, still accurately find their way.
Rainbow trout are one of them that navigates, at least partially, by polarized light.