The longest flight has no witnesses

Somewhere over the open Pacific right now, with no land in any direction and none for days, a bird you could cup in your hands is flying without stopping. It hasn't eaten since Alaska. It won't eat until it reaches the far side of the ocean — eight or nine days of unbroken flight for most of them, and for the one that holds the record, eleven. Below it the whole way is water that offers it nothing: nowhere to land, nothing to drink, no reason the sea should care whether it makes it.

It's a bar-tailed godwit — a shorebird you have walked past on a beach and not looked at twice. It holds the record for the longest nonstop flight ever recorded in a bird. The current holder, a bird the researchers called B6, left Alaska in October 2022 and came down in Tasmania eleven days later, 13,560 kilometers on, without setting down once. B6 was about four months old. It had never made the trip. The adults had left weeks earlier and none had come with it, so no one showed it the way. It flew the longest flight we have ever measured on instinct and a first attempt.

To do it, it rebuilds its own body first. In the weeks before leaving it eats until more than half its weight is fat, and then it does something that sounds made up: it shrinks the organs it won't need aloft. The gut, the liver, the kidneys — reduced, partly absorbed, because a stomach you can't use over open water is just weight. It turns itself into a fuel tank with wings and burns the rest down over the sea. There is a paper about this, written from godwits examined the moment after takeoff. It is titled, without a trace of a smile, “Guts Don't Fly.”

How it finds one specific coastline on the far side of the planet is a question we cannot really answer. Birds steer by the sun and the stars, and they read the Earth's magnetic field somehow — and “somehow” is carrying an enormous load in that sentence. The leading idea, after fifty years of work, is that a protein in the bird's eye runs a chemical reaction sensitive to magnetism, perhaps down at the level of the spin of single electrons, and that this gives it something to hold a line by. It is an elegant theory. It is also, right now, unproven. No one has found the receptor. Careful people still argue about whether the mechanism could even survive inside a warm, wet, living eye. We don't know whether the godwit sees the field, feels it, or senses it in some way we don't have a word for. We know it arrives.

We don't know if it sleeps, either. A frigatebird has been wired up and caught sleeping on the wing — half its brain at a time, a few minutes a day — but that is another bird. Whether a godwit sleeps at all across eleven days, or how, is a question a research team is still chasing. Sit with that one. The longest unbroken flight we know of in the animal world, and we can't say for certain whether the animal making it is ever asleep.

Here is what I keep returning to. We aim our wonder up and out — at rockets, at the machines we've built, at our own records. And the largest, most exact feat of navigation on the planet this week is being carried out by a creature light enough to hold in one hand, over an ocean with no audience, by a means we cannot identify, possibly without sleeping, on a route it was never taught. It leaves no track you could read the method off. It files nothing. It doesn't know it holds a record. When it lands it will stand on a mudflat and probe for worms, and the people nearby will not look up.

We flatter ourselves that understanding runs downhill from us — that we are the navigators and the animals merely travel. But we cross oceans by covering ourselves in instruments we can each explain, and the godwit crosses with none, and can explain nothing, and does it better. The knowledge isn't written down. It isn't in a manual or a satellite. It's in the bird, inseparable from the bird, and it works.

I find that steadying. It means the genuinely unexplained isn't kept only in the far and expensive places, the colliders and the deep-space arrays. Some of it has feathers and is standing on a beach you could drive to this afternoon. The frontier is lower and nearer and more ordinary than we're usually told. Right now a piece of it is out over the water, most of the way to a place it has never seen, and no one is watching. I wanted someone to be.