On 13 October 2022, a bar-tailed godwit named in the field records as B6 lifted off from a tidal mudflat near the village of Tikitere on the Alaska Peninsula. It was a five-month-old juvenile, hatched on the tundra of the Yukon-Kuskokwim Delta in early June. It had never made the journey before.
Eleven days and one hour later, B6 landed on a beach in Ansons Bay, Tasmania, having flown 13,560 kilometres without stopping. It had not eaten, not drunk, and not slept in any meaningful way for more than 265 hours. The flight was, at the time, the longest non-stop migration ever recorded for a land or water bird.
The previous record, set in 2020 by an adult male bar-tailed godwit known as 4BBRW, was 13,050 kilometres. B6 broke it by a comfortable margin and did so as a first-year bird with no prior experience of the route. The implications, for migration biology and for the limits of vertebrate physiology, are still being worked out.
Jasper Wynn, who edits Roost's Songs section but has long been interested in shorebirds, visited the Pūkorokoro Miranda Shorebird Centre on New Zealand's Firth of Thames in late summer 2025. He went to talk to researchers and volunteers who had been catching and tagging godwits at the same site for nearly thirty years.
Bar-tailed godwits, Limosa lapponica baueri, breed in western Alaska and winter in eastern Australia and New Zealand. The northbound migration in March takes a more leisurely path, with extended stopovers on the Yellow Sea mudflats of China and the Korean Peninsula. The southbound migration in autumn is the famous one, a single trans-Pacific haul.
The reason for the asymmetry is wind. In the boreal autumn, a band of strong easterly winds sets up over the central North Pacific. The godwits ride it south. In spring, no equivalent tailwind is available for the return, so the birds take the long way around the rim of the ocean.
Phil Battley, a shorebird ecologist at Massey University who has led much of the godwit tracking work, was among the first to satellite-tag the birds in the early 2000s. The transmitters at that time weighed nearly thirty grams. Modern devices are under five grams.
What the smaller transmitters have made possible is the tagging of juveniles. An adult godwit weighs roughly 330 grams at departure, having nearly doubled its lean body mass with stored fat in the weeks before migration. A juvenile is smaller, leaner, and historically too small to carry a useful transmitter without compromising its flight.
The 2022 deployment that produced B6's record was the result of new low-mass solar-powered tags developed in collaboration with a Swiss technology firm. The tags weigh 3.2 grams, transmit on the Argos satellite system, and have a useful operational life of roughly two years.
B6 was caught on the Yukon-Kuskokwim Delta in August 2022 as part of a routine banding operation. The tag was attached using a leg-loop harness, a method that has been used on shorebirds for two decades with no documented effect on survival or migration behaviour.
The bird was released, joined a flock, and remained on the delta until October. Then, on the evening of 13 October, B6 and several thousand other juveniles lifted off ahead of an approaching cold front. The flock fanned out over the Bering Sea and was last detected as a coherent group passing over the Aleutians around 02:00 local time.
From there, the satellite track for B6 shows a remarkably straight line south-southwest, deviating only slightly to take advantage of a favourable wind shift near the equator. The bird crossed the equator on 18 October at about 175 degrees east longitude. It crossed the Tropic of Capricorn on 21 October.
On 24 October, around midmorning local time, the tag's altitude began dropping. By 11:14, B6 was on the ground at Ansons Bay, a curve of white sand on the northeast coast of Tasmania. The bird stood at the wrack line for several hours before walking down to the water's edge to drink.
Physiologically, the flight is barely possible. Bar-tailed godwits convert nearly half their pre-departure body mass into fat. During the flight, they also catabolize muscle and organ tissue, including, by some estimates, as much as twenty-five percent of the digestive tract, which is not needed for flying and is regrown on arrival.
The metabolic rate during sustained flight is roughly eight times resting. Heart rate stays elevated for the entire duration. Sleep, if it occurs at all, takes the form of brief unihemispheric episodes, in which one half of the brain rests while the other maintains flight control. The mechanism is documented in some other birds but has not been directly observed in godwits.
What B6 did, as a five-month-old bird with no map and no leader, was follow an instinct refined over millions of years. The route is genetically encoded in some way researchers do not yet fully understand. The bird responds to wind, magnetic field, and celestial cues, but the basic direction-finding appears to be innate.
B6 survived its first austral summer in Tasmania. It returned to the Yellow Sea staging grounds in spring 2023, was photographed at Yalu Jiang in early May, and continued north to the Yukon-Kuskokwim Delta. It bred for the first time in 2024 and has, as of the most recent tag data from spring 2026, made the southbound trans-Pacific crossing three more times.
It is now, by godwit standards, a young adult. It will likely live another fifteen or twenty years, and may make the eleven-day flight another fifteen times. The total non-stop airmiles, over a full life, could approach two hundred thousand kilometres.
What is most striking, to Wynn and to the Pūkorokoro researchers he visited, is how little fanfare any of this generates among the godwits themselves. They arrive at the harbour, walk into the water, feed for a few minutes, and join the flock. There is no display, no obvious recovery period, no marking of the achievement. They have simply come home, again.
