It's not so much whether migrating birds and other living things detect magnetic fields then react like magnets, it's more a question of how creatures experience their migration. Which is a dilemma, because while by some wizardry of science I might be able to see through the eyes of a docile Homing Pigeon, I can never actually be a Homing Pigeon or an Arctic Tern or a Walrus. Nor will I ever know what it is to be a Tyrant Flycatcher, happy to be home and then chased by resident armies of Mockingbird. I can never actually be anything other than the rapidly ailing and tick ravaged thing which is me, and who should at this moment be outside euthanizing last year's Chard. And, luckily for the Summer Tanager up there wondering what happened to his Sycamore Tree, he can never know what it is to be me.
Of course pathways between magnet sensitive cells, emotion and behavior, in conjunction with seasonal changes will probably be mapped. Then, for a small monthly fee, this map can be prodded into the service of those of us who get depressed when the Swallows leave. Which means the science of migration can shout, "eureka, we can pay off the mortgage at last." But more important than the facts of how and why something happens, is the fact that it does happen. A conundrum which may or may not be solved by mathematics. And this is a conundrum that I experience as cheerfulness conjoined with a certain contentment, that some might call smugness, but which is probably more like peeing off the front porch. Which is a something I will go and do now, because for reasons totally beyond my comprehension, tomorrow I return to weekends of so called "gainful employment."