It shrinks its own gut, never lands and flies for 11 days straight: the bird that crossed the Pacific from Alaska to Tasmania

On 13 October 2022, a young bird with a satellite tag on its lower back lifted off from western Alaska and headed south over the open Pacific.

It did not stop. It could not: godwits cannot land on water, and cannot take off from it. For 11 days and one hour it flew on, past the islands of Vanuatu and New Caledonia, until it came down at Ansons Bay on the north-east coast of Tasmania. The tag, numbered 234684, showed it had covered 13,560 kilometres, about a third of the way around the planet, and beaten the previous record, set by another godwit in 2020, by more than 350 kilometres.

The bird was about five months old. It was its first migration.

How can a bird fly that far without food?

By turning itself into a flying fuel tank. Godwits spend weeks before departure feeding hard on the Alaskan coast, and the fat they lay down becomes most of what they are. Researchers studying Alaskan godwits about to leave found fat made up roughly 55 per cent of their body mass, among the highest fat loads recorded in any bird.

To make room, and to cut weight, they shrink the parts of the body that are useless in flight. In a landmark 1998 study, the Dutch biologist Theunis Piersma and the US Geological Survey’s Robert Gill found that godwits about to cross the Pacific had very small gizzards, livers, kidneys and guts compared with birds of the same species at other stages of the year. They titled the paper “Guts don’t fly”.

At the same time, the heart and flight muscles grow. When the bird lands on the other side, it rebuilds its digestive system and starts eating again.

Eric Woehler of BirdLife Tasmania estimated that the record-breaking bird lost about half or more of its body weight on the way.

How does a bird find Tasmania across an empty ocean?

Scientists do not fully know, and the record flight may have been partly a mistake. Most Alaskan godwits fly to New Zealand. Bird 234684 made a sharp turn and kept going to Tasmania, which Dr Woehler suggested was a “wrong turn” that shows the birds can fly even further than anyone had assumed.

What is known is that they choose their moment. Satellite tracking led by Dr Gill, published in 2009, showed godwits time their departures from Alaska to ride strong tailwinds from passing weather systems. In that study, seven tagged females flew nonstop for between 8,117 and 11,680 kilometres, taking between six and 9.4 days. The longest of them, a bird known as E7, flew from Alaska to New Zealand’s North Island in 2007, a record that stood until 2020.

The finding changed how scientists think about oceans. The Pacific, long assumed to be a barrier to land birds, works for godwits more like a highway with a reliable wind behind it.

How does it compare with other animal journeys?

Some animals travel further in total. None goes further without stopping.

| Traveller | Journey | Stops? | |—|—|—| | Bar-tailed godwit 234684 (2022) | 13,560km, Alaska to Tasmania, 11 days 1 hour | None | | Bar-tailed godwit E7 (2007) | 11,680km, Alaska to New Zealand | None | | Arctic tern | Up to about 80,000km round trip in a year | Lands and feeds along the way | | Qantas Perth to London, nonstop | About 14,500km, about 17 hours | None, but refuelled before take-off |

The Qantas comparison is the one that tends to stop people. The longest nonstop passenger flights from Australia need a 250-tonne aircraft. The godwit, which weighs a few hundred grams, comes close to matching that distance on fat it built up on a beach.

Why are Australia’s shorebirds in trouble?

Most of Australia’s migratory shorebirds travel along what scientists call the East Asian-Australasian Flyway, breeding in Siberia and Alaska in the northern summer and spending the southern summer here. Many stop on the way north at the tidal mudflats of the Yellow Sea, between China and the Korean Peninsula, to refuel.

Those mudflats are disappearing. A 2014 study led by Nicholas Murray, using satellite images, found that 28 per cent of the Yellow Sea’s tidal flats present in the 1980s had gone by the late 2000s, mostly to land reclamation, and that historical maps suggested up to 65 per cent had been lost over five decades. A 2017 study in Nature Communications found that seven of 10 shorebird groups that rely on the Yellow Sea were declining, some by up to 8 per cent a year.

In 2016 the federal government listed the Alaskan godwits that come to eastern Australia and New Zealand as vulnerable, and the northern Siberian godwits, which spend the southern summer mainly in north-west Australia, as critically endangered. The far eastern curlew, the world’s largest shorebird, is also listed as critically endangered nationally.

Why does it matter to anyone who isn’t a birdwatcher?

Because these birds are a running measure of the health of coastlines from Alaska to Western Australia. A godwit needs intact mudflats at every end of its journey: lose a feeding site in the Yellow Sea and birds that have just flown thousands of kilometres arrive with nothing to eat.

They are also fragile in a very ordinary way. A bird that has just crossed an ocean is running on empty. Every time a dog, a person or a vehicle flushes a resting flock off a beach, the birds burn energy they need to rebuild their bodies and fuel the flight home.