Magnetic cells key to animal migration

[chknltl]

2. I have long wondered about that.

I know salmon about to spawn use a sense of "smell" to navigate with when they near the river of their birth. What I was perplexed by was how they navigated there from the open ocean.

This magnetic cells revelation leads me to wonder if the entire earth is covered in an unseeable magnetic map, one with micro-variations that these cells can detect. Perhaps these micro variations change with the earth's rotation around the sun, which might be what these migrating creatures are following.

By now the earth has been mapped every way to Sunday by satellites, likely down to those magnetic microvariences if they do indeed exist.. Perhaps a study could be made where migration routes are matched up with the earth's magnetic field fluctuations and microvariations.