In October 2022, a five-month-old bar-tailed godwit fitted with a satellite tag by the U.S. Geological Survey lifted off from southwestern Alaska and did not land for 8,425 miles. Eleven days later it touched down in Ansons Bay on the northeast coast of Tasmania, having crossed the entire Pacific Ocean nonstop. The tracker recorded a roughly 13,560 kilometer flight, which the USGS and the Max Planck Institute of Animal Behavior described as the longest continuous flight ever documented for any animal.
The bird had never made the trip before. It had no parents leading the way, no peer convoy, no land in sight for most of the journey. It also did not eat or drink for the duration. Researchers studying the species have spent two decades trying to explain how a creature weighing less than a pound pulls this off, and the answer involves shrinking organs, controlled muscle catabolism, and a navigation program written in a five-month-old’s genes. The honest version of the story is stranger than the headline suggests.1
What is a bar-tailed godwit, exactly?
The bar-tailed godwit (Limosa lapponica) is a long-legged shorebird with a slightly upturned bill and a streaked brown body that blends into mud and dune grass. The subspecies that nests in western Alaska, L. l. baueri, is the one with the absurd flight log. Adults weigh somewhere between 250 and 450 grams depending on the season, which is to say between a small apple and a hardback novella.
For most of the year they are unremarkable to the casual eye. They probe tidal mudflats for marine worms and shellfish, they gather in loose flocks, they get gradually plumper. The remarkable part is what that plumpness is for. By late September, an adult Alaskan godwit can be more than half body fat by weight, which is a level of obesity that would kill almost any mammal and that the godwit treats as a warm-up.3
How does a bird fly for 11 days without sleeping?
Honestly, scientists still argue about the sleep part. There is decent evidence that some long-distance migrants take micro-naps in flight, shutting down one cerebral hemisphere at a time while the other keeps the wings going, but the godwit literature is more cautious. What is clear from satellite tracking is that the birds rarely break their flight even when ocean weather turns rough.
The endurance side of the question has cleaner answers. Long-distance migratory birds do not power their flight muscles the way a sprinter does. They run almost entirely on fat oxidation, which yields about nine kilocalories per gram, more than twice the energy density of carbohydrate or protein. Bar-tailed godwits push that strategy further than almost any other studied bird. In a foundational paper on godwit metabolism, Landys and colleagues showed that birds in active flight rely overwhelmingly on stored triglycerides, with plasma free fatty acids and ketone bodies climbing across the journey while carbohydrate use stays minimal.3
Storing that much fuel creates a packaging problem. A bird is not a fuel tank with wings; it is an animal with kidneys and a liver and a digestive tract that all take up space and metabolic budget. So godwits do something most vertebrates cannot.
The body that eats itself
In the weeks before departure, bar-tailed godwits shrink the organs they will not need in the air. The gizzard, intestine, kidneys, and liver all reduce in mass, sometimes by a quarter or more, freeing up cavity space and lowering basal metabolic cost. The pectoral flight muscles, by contrast, hypertrophy. Researchers have called this seasonal phenotypic flexibility, and it is one of the cleanest examples in vertebrate biology of an animal redesigning itself in real time for a single task.
Once the flight begins, the consumption keeps going. The bird is, in a literal sense, eating itself. Fat goes first. When fat reserves run thin, godwits start drawing on protein from those bulked-up flight muscles, a process Guglielmo and colleagues compared to the muscle damage seen in extreme human endurance sport.4 Plasma markers of muscle breakdown rise during the flight and then drop sharply once the bird lands and starts feeding again. A godwit that touches down in New Zealand or Tasmania has, in effect, partially digested its own thighs.
Calling that a tragedy misses the point. The breakdown is part of the design. The protein is rebuilt at the wintering grounds, the digestive organs grow back over a few weeks of solid eating, and by April the bird is plumping up again for the return leg.
Why does this bird not stop on islands?
You would think a sensible bird would island-hop. The Pacific has stepping stones. Hawaii is roughly halfway. Fiji and New Caledonia sit conveniently along plausible routes south. Plenty of other migratory species do exactly that.
Bar-tailed godwits do not, and the reason is mostly arithmetic. Stopping costs energy. Landing, refueling for days or weeks, and taking off again all burn fat that could have gone into staying airborne. Worse, suitable shorebird habitat in the central Pacific is scarce, and the birds would arrive at small islands that may not have the prey biomass to refuel a 300 gram passenger. Some islands also carry predator risk, including introduced rats and cats that hammer ground-nesting and ground-resting birds.
So the godwit’s strategy is the counterintuitive one: skip the layovers entirely. A nonstop flight on stored fuel turns out to be cheaper, in a strict caloric sense, than a multi-leg trip with refueling stops, provided the bird has banked enough reserves at takeoff. The Alaskan staging grounds, especially the Yukon-Kuskokwim Delta, are the gas station for the entire crossing.5
How does a five-month-old bird find Tasmania?
This is the part that bends most people’s brains. The juvenile that flew 8,425 miles in 2022 was hatched in Alaska earlier that summer. It had never been to the southern hemisphere. Adults departed before juveniles, so it had no flock to follow.
The honest answer is that researchers do not have a complete explanation. What they have is a list of cues that the birds appear to use in combination. Godwits are sensitive to the Earth’s magnetic field, both intensity and inclination, and laboratory work on related shorebirds suggests they use it as a coarse compass and possibly as a map. They also seem to integrate the position of the setting sun and stellar patterns, the direction of prevailing winds at the altitudes they fly, and a strong genetic component that biases their first migration in the right general direction. Conklin and colleagues, working with long-term godwit data, have argued that individual birds carry an internal program that is remarkably consistent year after year, with departure dates, route choices, and arrival dates clustering tightly within an individual even as it shifts plastically across years.12
That last point matters. Earlier research framed migration timing as either innate (genetic) or learned (cultural). The godwit data points at something more interesting: an innate framework with built-in flexibility, allowing a bird to adjust to a warmer spring or a delayed feeding window without abandoning the larger plan. It is closer to a pre-loaded operating system than to a printed map.
It is not just one bird
The 13,560 kilometer flight made the headlines because it was a record, but the record-holder is not unusual in kind. Adult bar-tailed godwits routinely fly between 11,000 and 12,000 kilometers nonstop on the southbound autumn leg from Alaska to New Zealand and eastern Australia. Battley and colleagues, working with satellite-tagged birds, documented multiple individuals making nine to ten day continuous crossings of the Pacific in successive years, with each bird returning to the same wintering site, often the same square kilometer of estuary.2
Site fidelity at that level, repeated over the decade-plus lifespan of an individual godwit, is now well documented across the East Asian-Australasian Flyway. A 2023 satellite-tracking study of multiple shorebird species in the same flyway found that individuals returned to specific staging mudflats with such consistency that habitat loss at any one of those sites caused detectable drops in survival, even when the rest of the flyway looked healthy from above.5
That is the quiet sequel to the headline. A godwit’s nonstop endurance is breathtaking on its own. The sting is that the species’ entire life cycle depends on a thin chain of specific places, most of them coastal mudflats currently under pressure from reclamation, sea level change, and aquaculture. The world’s most extraordinary athletes are also some of its most habitat-dependent.
Does the bird actually feel exhausted?
You cannot exactly poll a tired godwit, but the physiological signs are there. Birds arriving at southern wintering grounds after a multi-day Pacific flight are visibly thinner, their pectoral muscles smaller, their plasma chemistry altered in ways consistent with severe energy depletion and tissue catabolism. Recovery takes weeks. During that period the birds eat almost continuously, and in lab studies of related species the digestive organs that shrank before takeoff regenerate at impressive speed once feeding resumes.34
So it is fair to say the godwit pays a real price for its trip. It does not glide effortlessly across the Pacific the way a casual reading of the headline might suggest. It arrives broken, and then it rebuilds, and then it does it again, and then it does it again, year after year, for as long as it lives. Some banded individuals have been re-sighted across more than a decade of round trips.
Common questions about the bar-tailed godwit’s flight
How fast does the bar-tailed godwit fly?
Tracked ground speeds vary with tailwinds. Across the southbound transpacific leg, average speeds have been recorded between roughly 50 and 90 kilometers per hour, with strong following winds occasionally pushing individuals faster.
Does the bird sleep during the flight?
It probably takes brief uni-hemispheric naps, where one half of the brain rests while the other stays alert, a pattern documented in some other long-flying species. Godwit-specific sleep data in flight is still limited.
How much weight does it lose?
Birds can lose roughly half their pre-departure body mass over a multi-day flight, with most of the loss coming from fat and a substantial fraction from protein in the flight muscles and digestive organs.
Is the species endangered?
The Alaskan-breeding subspecies, L. l. baueri, is currently listed as Near Threatened, with population declines tied largely to habitat loss at staging mudflats along the Yellow Sea, not to the migration itself.
How can a juvenile know the route on its first try?
Genetic predisposition appears to set a default heading and timing window, while real-time cues, magnetic, celestial, and meteorological, refine the route. The bird is not consulting memory; it is running a program shaped by tens of thousands of generations of selection.
Where this leaves us
Calling the godwit’s flight impossible is wrong, and it is also the right instinct. The trip is impossible for a creature built like us, with our intestines and our metabolic floor and our refusal to digest our own muscle. It is routine for a creature built like a godwit, and even that routine sits closer to the edge of what biology can do than almost anything else in the animal world.
The bird that landed in Tasmania in 2022 was not a miracle. It was an animal that had paid attention, in the way evolution pays attention, for long enough to encode a Pacific crossing into the pattern of its own organs. Next time you see a small brown shorebird working a mudflat, slow down for a second. There is a fair chance it has flown farther without stopping than you will fly in your life with a fleet of jets at your disposal.
Sources
- Conklin JR et al. Advancement in long-distance bird migration through individual plasticity in departure. Nature Communications, 2021. PubMed: 34362899
- Battley PF et al. Consistent annual schedules in a migratory shorebird. Biology Letters, 2006. PubMed: 17148277
- Landys MM et al. Metabolic profile of long-distance migratory flight and stopover in a shorebird. Proceedings. Biological Sciences, 2005. PubMed: 15705555
- Guglielmo CG et al. A sport-physiological perspective on bird migration: evidence for flight-induced muscle damage. The Journal of Experimental Biology, 2001. PubMed: 11533118
- Chan YC et al. Site fidelity of migratory shorebirds facing habitat deterioration: insights from satellite tracking and mark-resighting. Movement Ecology, 2023. PubMed: 38129912
