The longest flight
The bar-tailed godwit makes the most extraordinary journey of any animal on Earth. Each spring it arrives in New Zealand half-dead. Each autumn it leaves again. A small, devoted community of New Zealanders has built their lives around watching this happen.
The first birds usually appear in the second week of September, though nobody can predict the day. They arrive at Pūkorokoro Miranda before sunrise, dropping out of a clear sky onto the Firth of Thames in ones and twos and small ragged groups, and the people who have been waiting for them — and there are always people waiting — describe the same thing every year. The birds don’t circle. They don’t survey their landing site. They drop straight onto the shell banks they left in March, fold their wings, and go to sleep.
A bar-tailed godwit at the moment of arrival has been awake and airborne for somewhere between eight and eleven days. She has flown roughly eleven thousand kilometres, non-stop, across the open Pacific. She has not eaten since Alaska. She has not drunk water. She has lost half her body weight in flight muscle, fat, and the parts of her own digestive system her body cannibalised for fuel along the way. Her flight feathers, which were pristine when she lifted off the Yukon-Kuskokwim Delta in early September, are frayed at the edges. The leading edges of her primaries are worn translucent. If you handle her — and the licensed banders at Miranda do, gently, briefly — you can feel her keel bone through the skin. There is almost nothing left of her except the muscle that flew her here.
Then she sleeps for the better part of a day. Then she walks down to the mudflats on the falling tide, finds a bristle worm, and eats it. The journey is over. She has another six months in New Zealand before she has to do it again.
This is the longest non-stop flight made by any animal on Earth, and it has been happening, as far as anyone can tell, for tens of thousands of years.
Pūkorokoro Miranda Shorebird Centre is a low timber building set behind the seawall on the western edge of the Firth of Thames, ninety minutes south-east of Auckland by car. It is run by a small permanent staff and a much larger contingent of volunteers, most of them retired, all of them serious. The carpark fills up in spring. A noticeboard inside the door tracks arrivals — first birds 12 September, flock of 40 by Tuesday, 200+ by weekend — in handwritten marker pen, the way an earlier kind of newsroom might have tracked a developing story.
The centre exists because of a single intuition, repeatedly tested and proven correct, which is that if you give people a hide and a pair of borrowed binoculars and ten minutes of someone explaining what they are looking at, a meaningful number of them will become bird people for the rest of their lives. It has been proving this since the late 1970s. Several thousand New Zealanders are godwit-attentive in some serious way because of Miranda. Almost all of the data science we have on the migration — the satellite tags, the leg-flag resightings, the body-condition surveys — comes through the centre or its international partners.
The carpark has its regulars. There is a particular subset of New Zealand birding, and birding-adjacent retirement, that involves following godwit arrivals up and down the country in a campervan, and the same small fleet appears at Miranda each September and at Farewell Spit each January and at Awarua Bay near Bluff in February. They know each other. They know the birds, after a fashion — not as individuals, mostly, but as flocks with characters: the early-arriving Manukau group, the late-leaving Firth contingent, the small persistent bunch that overwinters at Awarua some years instead of flying north. They keep notebooks. They keep WhatsApp groups. Several of them keep blogs that have been running since the early 2000s and which contain, in aggregate, a more granular record of New Zealand’s godwit population than any official source.
Most of them freedom-camp along the beach. The Seabird Coast road runs north from the centre with a long ribbon of foreshore on its eastern side, and in the weeks after the godwits arrive a loose community of vans assembles along it — a few dozen at peak, parked nose-to-tail facing the Firth, awnings out, kettles on. Some stay for a night. Some stay for the season. The arrangement is unofficial and more or less self-policing; the godwit people are tidy by demographic and the locals tolerate them. A smaller contingent peels off and stays at the Miranda Holiday Park instead, and the reason is almost always the hot pools next door — Miranda’s geothermal springs, which were drawing visitors before the shorebird centre existed and which give the place its incongruous second identity as a soaking destination. There is a particular kind of evening, after a high-tide watch in cold spring weather, that ends naturally in a hot pool. The holiday-park birders know this. The freedom campers, as a rule, are tougher, or at least claim to be.
The post-watching ritual, for everyone, is the fish and chip shop at Kaiaua. Kaiaua is a small coastal settlement about ten minutes north of the centre along the Seabird Coast road, and the fish and chip shop there is the kind of unpretentious roadside takeaway that has somehow, over time, become institutional. The birders go after the high-tide watch. The hot-pool soakers go after the soak. The day-trippers from Auckland stop on their way home. The shop sits opposite the beach with a few outside tables, and on a weekend in October the queue stretches out the door and is composed almost entirely of people who have spent the morning watching shorebirds, in various combinations of fleece and binoculars and damp togs, eating chips out of the paper while looking at the water the godwits arrived across.
The campervan birders are easy to caricature, and people do, but it is worth saying clearly: they are paying attention to something that almost nobody else is paying attention to, in a country whose ecological story is largely the story of what stopped paying attention in time. They are unpaid. They are mostly unread. Several of them are, in any reasonable sense, citizen-scientists of the first rank. The peer-reviewed paper that established E7’s record-breaking 2007 flight had the centre’s volunteers in the acknowledgements; those volunteers were the ones who saw her leg flag through a spotting scope on the Miranda shell banks the day after she landed, and reported the sighting to the researchers in Alaska who had been wondering where she’d gone.
What they are watching for, in September, is one of those moments when a piece of the natural world becomes legible. The arrival is sudden and concentrated and unmistakable. One day there are no godwits in New Zealand. The next day there are forty thousand. You can stand on the seawall at Miranda at the right hour and watch them come in across the Firth in long low skeins, calling — a soft musical kuek that carries further than it should — and the air on the shell banks fills up with birds that were not there yesterday and that have just arrived from the other end of the planet.
To understand what these birds have done, it helps to think about what they are made of when they leave Alaska.
A bar-tailed godwit at her staging weight is not a normal animal. A non-migrating shorebird of her size weighs about two hundred and fifty grams. A pre-migration godwit weighs six hundred. The difference is fat — pure, dense, slow-burning fat laid down on the breast, the flanks, the abdominal cavity, even the wishbone. Half her body, by mass, is fuel.
She also reorganises her own anatomy in the weeks before departure. The digestive organs she will not need in flight — the gizzard, parts of the intestine, the liver — are partially reabsorbed, shrinking to a fraction of their normal size. The flight muscles, by contrast, grow. Her heart enlarges. Her lungs become more efficient. By the time she lifts off she is essentially a flying engine bolted to a fuel tank, with the minimum biological apparatus required to keep both running. When she arrives in New Zealand she will spend her first weeks rebuilding the organs she dismantled to get here.
The flight itself is poorly understood, because for most of human history nobody could observe it. Until the satellite tags, we knew the birds flew non-stop because they had to: there was no land between Alaska and New Zealand where a shorebird could refuel, and they showed up in New Zealand each spring without anyone ever seeing them on the way. The tagging program at Miranda, beginning in 2007, replaced inference with measurement. The first tagged bird, E7, flew from Alaska to the Miranda shell banks in eight days and twelve hours. The data was so unprecedented that the team double-checked the satellite fixes before publishing.
What the tags show is this. The birds wait in Alaska through August for the right weather. They are looking, specifically, for the back end of a Bering Sea low-pressure system — a southerly-spinning storm whose trailing edge produces a strong tailwind across the central Pacific. When the window opens they leave en masse, often within a few hours of one another, climbing fast to between two and three thousand metres and turning south. They cross the equator on the fifth or sixth day. They sight the New Zealand coast on the seventh or eighth.
In flight they sleep one cerebral hemisphere at a time, the way dolphins do. They fly through the night as well as the day. They navigate without landmarks — there are none — by some combination of an internal magnetic compass, the position of the stars, and possibly the polarisation pattern of light in the sky at sunset. None of these mechanisms is fully understood. The birds also appear to be able to read the wind systems beneath them and adjust altitude to find favourable layers; tagged birds frequently climb or descend several hundred metres at apparent decision points, and the tracks suggest these adjustments save fuel.
By the final two days of the flight the birds are in serious deficit. Their fat is largely burned. They are running, increasingly, on muscle protein. Their flight speed drops from around eighty kilometres per hour to nearer fifty. Some birds, every year, do not make it. The tags occasionally go silent over the open Pacific in the last three or four days of a flight, and the researchers note the loss. Most reach New Zealand. The arriving birds are, by any veterinary measure, in a state that would be classed as catastrophic in a domestic animal — emaciated, dehydrated, exhausted, with measurable damage to the heart muscle and the kidneys. Then they sleep. Then they eat. Within two weeks they are functionally normal birds again, and within six they have replaced most of the fat and muscle they lost. The body, having survived this once, prepares to do it again.
The northbound migration in March is the harder one, although it gets less attention.
The southbound flight from Alaska to New Zealand is non-stop because there is no choice — there is nowhere to land. The northbound flight, which leaves New Zealand in late March, is broken into stages, and that turns out to be its vulnerability. The birds fly first to the Yellow Sea, the great enclosed bay between China, North Korea and South Korea, where they have for thousands of years refuelled on the intertidal mudflats before pushing on to Alaska. A godwit arriving in the Yellow Sea in April is in roughly the same state as one arriving in New Zealand in September. She needs a month of intensive feeding on shellfish and worms to rebuild her body for the second leg.
The Yellow Sea mudflats have lost more than two thirds of their area since the 1950s. The reclamation projects around Shanghai, Tianjin, the Yalu River estuary and Saemangeum on the South Korean coast have buried under landfill what were, in measurable terms, some of the most productive shorebird feeding grounds on the planet. Saemangeum alone, completed in 2010, eliminated 401 square kilometres of intertidal flat — about one-fifth of the bar-tailed godwit’s known refuelling habitat. Survey data taken before and after the closure shows a corresponding crash in returning bird numbers. The birds did not relocate. They simply did not return.
The birds you see at Miranda in September are the survivors of a system that is being dismantled. They are also the parents and grandparents of birds that will not exist if the system continues to be dismantled. The northbound flight is the bottleneck. Fix the Yellow Sea and the bar-tailed godwit’s population stabilises. Lose the rest of the Yellow Sea and they are gone, and with them the longest flight in the natural world.
International conservation work has slowed the loss but has not stopped it. South Korea’s national government has, in the last several years, announced halts to some reclamation projects. UNESCO inscribed several Yellow Sea tidal flat sites as World Heritage in 2019 and again in 2024, and the Chinese government has, with caveats, joined the effort. Researchers who have spent their careers on this — many of them affiliated with Miranda or its international partner the Global Flyway Network — describe the situation as cautiously improving and still not safe. The birds depend on decisions made by governments thousands of kilometres from where they spend most of their lives, and on decades-long international cooperation that nobody can guarantee.
This is a difficult thing to explain on the seawall at Miranda in September, when the birds are arriving and the flock on the shell banks is a noisy chaos of feathers and the new arrivals are sleeping. The volunteers explain it anyway, several times a day, to whoever is there.
There is a phrase in te reo Māori, kua kite te kohanga kuaka? — who has seen the nest of the godwit? — which is asked, traditionally, of someone claiming impossible knowledge. The phrase pre-dates any human understanding of where the godwits went each autumn. For centuries before the satellite tags, before the first European observations, before anyone in New Zealand had any reason to suspect that the same birds returned year after year from the same place, the kuaka were known here as creatures whose origins were not knowable. They arrived. They left. Nobody saw their nest. Nobody saw them breed. The whakataukī attached the birds, in the cultural imagination, to the spirit world and the territory of things that could not be witnessed.
The satellite tag is, in this sense, an answer to a very old question. We now know where the godwit’s nest is. It is on the western coastal plain of Alaska, in shallow scrapes lined with grass and lichen, mostly within a few hundred metres of the sea, at latitudes around sixty-five degrees north. We know what the eggs look like. We know which males brood them. We have video of the chicks. The birds are no longer the unknowable creatures of the whakataukī. But the journey they make twice a year between the two ends of the Pacific has become, if anything, more astonishing the more we have measured it. The distance is greater than we thought. The physiological cost is more extreme. The navigation is less explicable. The whakataukī’s underlying intuition — that these birds belong to a world larger and stranger than the one we walk around in — turns out to have been correct, just not in the way the people who first said it had in mind.
In late February, when the birds are getting ready to leave again, there is a ceremony at Miranda. It is small. It is unscripted. The volunteers walk down to the seawall in the late afternoon, and any visitors who happen to be there walk down with them, and they stand and watch the flock. The birds at this point are at peak weight again — fat, restless, increasingly vocal in the days before departure. They have been seen to test the wind in small flights along the shoreline. The volunteers know what they are watching for, which is the moment a flock decides to go.
The going, when it happens, is unmistakable. The flock lifts off the shell banks together. They climb in a tight formation, calling, and turn north. Within minutes they are high enough to be silhouettes. Within an hour they are gone. There may be ten thousand birds in a single departing flock, and the air after they have left is, by general agreement among the people who have watched this many times, briefly very quiet.
The campervan birders go home. The carpark empties. The handwritten board inside the centre is wiped, and a new one starts: first northbound departures 22 March, last birds gone by 4 April. Someone marks the date on the calendar at the back of the office. September is six months away.
In Alaska, in May, on the Yukon-Kuskokwim Delta, the same birds will land on the same coastal plain they left in September. They will breed. They will moult into their summer plumage, brick-red and beautiful, which is a colour New Zealanders almost never see because by the time the birds reach New Zealand they have moulted again, into the muted browns and greys they wear on the mudflats. They will raise chicks. They will eat berries. They will gain weight, again, through August, watching the weather. And on a clear morning in early September, with a Bering Sea low-pressure system breaking up and a southerly wind setting in, they will lift off the Alaskan tundra together and turn south, and a small group of New Zealanders in a carpark on the Firth of Thames will be ready, again, with binoculars and spotting scopes and a noticeboard waiting to be filled in, to watch them come home.
An interactive visualisation of a single tagged godwit’s southbound migration, compiled from satellite tracking data, is available at newswire.co.nz/data/kuaka.