Flying for their lives

Updated

Every year, millions of shorebirds fly between Australasia and the Arctic. But for many, this will be their last flight.

The first experience of Australia, for most international visitors, is an area of destroyed shorebird habitat: Sydney's Kingsford Smith Airport.

This flat tidal zone once provided a feeding point for thousands of migratory shorebirds. The birds still come, but in far smaller numbers.

The birds come to Botany Bay, and other mudflats across Australia and New Zealand, every year to eat. They aim to get so fat that they'll start to look like feathered sumo wrestlers.

They're migrating to chase an eternal spring and summer — and the seasonal blooms of food that come with it: the Arctic Circle's mosquito boom in June and July; Yellow Sea mudflats teeming with shellfish in April and May; and the shores of Australasia in November and December.

The act of migration isn't exceptional, but the distance of this one is. In 2007, a female bar-tailed godwit was tracked flying 11,680 kilometres from Alaska to New Zealand in nine days straight. It is the longest recorded bird flight on the planet.

It seems perverse that a bird that can fly far enough to get to the moon in its lifetime should be so fragile, but the bar-tailed godwit and its fellow shorebirds—snipes, stilts, stints, turnstones and curlews, among others—face enormous, perhaps insurmountable, challenges.

The populations of the eastern curlew and the curlew sandpiper have declined by more than 80 per cent in the last 50 years, and seven of Australia's 37 migratory wader species are edging towards extinction.

Shorebirds are not seabirds, they are waders—without webbed feet, they only go into the water as long as they can touch the bottom. So they survive in a place in between the sea and the land: the area revealed each day between high and low tide.

This type of habitat exists all along the East Asian-Australian Flyway, the migratory shorebird highway that 8 million birds use to travel from Australia to the Arctic Circle. It takes in 22 countries, from Bangladesh and Myanmar in the west; to Australia and New Zealand in the south; and Russia, Alaska and Korea in the north.

And all along this route, intertidal zones are under threat. The flyway is on the brink of collapse.

Food, glorious food

The Wiggins Coal Terminal looms on the Queensland mainland, separated from nearby Facing Island by a few kilometres of water and tidal flat.

It's one of Australia's major coal export hubs. Enormous tankers sit in the water, lining up to take on their cargo and bring it up the flyway to China.

Not far away, a critically endangered eastern curlew stalks the tide, probing the muddy flats. In a few short months, it too will leave for the Yellow Sea. But, unlike the tanker, it will be under its own steam.

Observing them is Richard Fuller, wet to his chest, muddy, and dragging a makeshift sled across the mudflat.

The University of Queensland academic and his team are trying to find out what birds like the curlew are sucking up when they stick their beaks in the mud.

Shorebirds have evolved to be specialised feeders; each species will have a different leg length and its own idiosyncratically shaped bill.

Some are curved, for poking down sloped holes in the mud; others are short, for picking prey off the surface; and others still are long and with touch-sensitive tips, for locating animals deep in thick mud.

These adaptations spread the feeding load across the mudflat so that different species do not compete for a single food source. But in the modern world, these ingenious and specific adaptations are also dangerous; if a habitat is disturbed and there is no prey, birds die.

"It's really death by a thousand cuts," Fuller says, looking across the water. "So 'a piece gone here, a piece gone there' can build up over the years to substantial impacts.

"These birds aren't just declining in the abstract sense, they're heading towards extinction. Every time a species goes extinct, we lose something that we can't get back."

We have liftoff

On the other side of Australia, in Broome, a different species of migratory shorebird — the red knot — is preparing to migrate.

Across the mudflats, the knots stand resolutely in a line spread out east to west as if waiting for a bus.

Internally though, they are anything but calm. Even their organs are getting ready for the trip: their gizzard and liver are contracting, and their heart is becoming larger to deal with the physical exertion to come.

Around them, mudskippers flip along, fiddler crabs wave their red claws at each other and other shorebirds scramble, probing the mud.

They stand legs slightly askew, accommodating their newly formed bird-guts. They will use this creamy-yellow, energy-rich fat to fuel their flight to the other side of the world.

Virtually as one, the knots all lift from the mudflat, calling out a rallying song. They circle, gaining altitude, and form a wide echelon.

Chris Hassell, an ecologist with the Global Flyway Network, perches on a stool and watches the birds through a telescope.

"I'm looking at a Red Knot there which is code three, blue lime/blue blue, 50 per cent breeding plumage," Hassell says, noting the details on a clipboard.

They flow over the red cliffs of Roebuck Bay, their wings pushing them slowly higher into the sky.

"I will probably see that bird in China."

An unusual welcome

Whimbrels circle in the air.

In the meadow below, surrounded by feathered decoys, Jin Weiguo sits, his umbrella propped up behind him, a cut bamboo whistle in his mouth.

Weiguo blows the thumb-sized instrument, controlling the sound with his tongue and lips, producing the squeals and trills of shorebirds.

The 57-year-old waits patiently as the birds lose altitude and touch down gingerly.

Violently, he pulls a thin rope attached to a long net. The net sails across the grass like a white wave. Caught by surprise, the birds flap and struggle, but cannot escape.

Weiguo, once a hunter, is now a trapper. He learned to whistle from his father when he was seven and has caught, by his own estimate, tens of thousands of shorebirds in his lifetime.

He used to sell them—for food, or as pets for children. A piece of string would be tied about their necks and they would be fed rice, Weiguo says.

Now he captures shorebirds on the island of Chongming, 50 kilometres out of Shanghai, so that researchers can weigh them, measure them, and tag them.

His transition from poacher to conservationist could be taken to be emblematic of an increasing concern about the natural environment in China.

But the reserve Weiguo works in sits surrounded not by greenways, but by industry, and deep sea ports.

After a period in hand, the birds are released with their coloured tags. Slightly dazzled, they spill into the smog-filled sunlight over the Yangtze River.

Hungry godwits, plovers and whimbrels stop here briefly from almost everywhere along the flyway: from Myanmar, Indonesia, India or Australia.

The mudflats here, fed by the Yangtze River, have provided food for birds and locals alike for thousands of years.

The Yellow Sea, between China and the Korean Peninsula, produces 20 per cent of the world's fishery products.

It supports endangered finless porpoises, Eurasian otters, largha seals, and millions of migratory shorebirds.

Or at least, it used to.

A new Great Wall

In the 10 years leading to 2013, seawalls have destroyed 1.36 million hectares of intertidal habitat in China.

Fifty-one per cent of China's coastal wetlands have now been lost, and the numbers are similar elsewhere. On the other side of the sea, South Korea has lost 60 per cent.

Of all the problems along the flyway, it is habitat loss on the Yellow Sea that poses the greatest threat to shorebirds.

It is also politically intractable: while the Yellow Sea laps against the shores of South Korea, North Korea and China, land reclamation is governed by individual nations.

"Nationally there is a very strict regulation on land use [in China]," says Professor Lei Guanchun, dean of the School of Nature Conservation at Beijing Forestry University.

"If you want to convert farmland into a construction area or urban development area, you need to have another piece of land to compensate."

This so-called "red line" law was intended to protect against famine by maintaining the amount of farmland in China, but has had the unintended effect of devastating the country's intertidal zones.

In the past, this effect has been multiplied — government bonuses were awarded for GDP growth, providing an incentive for reclamation and construction.

Worse still, much of the reclaimed shorebird habitat sits unused. For developers, it's just a column to be filled in a ledger.

Presently, almost 70 per cent of China's coastline is walled: 11,000 kilometres.

Sharing the mudflats

Coastal reclamation in the Yellow Sea eats the mudflat layer by layer, reaching further and further into the sea.

Humans have been doing this for thousands of years — it's only the pace that has changed. China's economic boom, and the shoreline reclamation that has gone along with it, has proved disastrous for shorebirds like the bar-tailed godwit.

In a 2008 study, satellite-tagged godwits from Australia were recorded stopping at Rudong, in the Jiangsu Province north of Shanghai.

By 2015, 90 per cent of sites the godwits used in 2008 had been reclaimed. It's not known exactly what happened to the birds, but since then both subspecies of bar-tailed godwits have been upgraded on the Commonwealth Threatened Species List.

It's not just birds that need this area to survive: local worm-pickers now use seawalls, some of which extend for kilometres, to access what's left of the mudflats.

The worms they collect are sold as fish food in Japan, but workers say that they too have felt the effect of reclamation and development.

The seawalls change the way the tides work; the mudflats and the organisms that live in them can be deprived of the nutrients and silt they need to survive.

Meanwhile, fertiliser and pharmaceutical factories sit along the shoreline, emitting the stench of rotten meat. A link between the rise of heavy industry and the decline in bird numbers has not been proven.

One woman says that worms are also in decline. The fish die, she says. The worms die. The clams disappear. The birds stand, wings drooping, unable to fly. They either fall over dead or drown in the oncoming tide, she says.

The next wave of seawall building will embrace 600 square kilometres of mudflats. It will be the largest reclamation in the world, and will envelope the intertidal zone around Tiaozini.

This whole area would become dry land: no shellfish, no tides and no shorebirds.

This process has already happened: in 2006, on the other side of the Yellow Sea.

Disaster on the flyway

South Korea's Saemangeum Seawall project cut off an estuarine tidal flat supporting an estimated 400,000 birds as well as at least 25,000 local people.

The 30-kilometre seawall at Saemangeum isolated a section of land five times the size of Manhattan for industrial and agricultural development.

At first there was an overabundance of food, as invertebrates opened their shells and died on the drying mud. But soon there was nothing, dead or alive, for the birds to eat.

The reclaimed land remains largely undeveloped. "To see it trashed for no reason is like sitting next to someone you love who is dying. It's devastating," says Dr Nial Moores, director of Birds Korea. "The vast majority of birds simply ceased to exist," he says.

That was felt in Australia: after the Saemangeum reclamation, the great knot population was reduced by 20 per cent in a single stroke.

The knots never made it back. But elsewhere on the Korean peninsula, shorebirds have found an unlikely sanctuary.

An unlikely saviour

North Korea's comparative lack of development has been a boon for the birds and for the researchers who track them.

"There's far less industrial pollution because there is far less industry along these rivers," says Adrian Riegen.

Riegen is a builder and bird watcher from Auckland who has devoted much of his life to shorebirds at New Zealand's Pukorokoro Miranda Naturalist Trust.

After working with Chinese officials to survey bird numbers at Yalu Jiang, Riegen and a small group from the trust approached the North Korean government to ask if they could assess habitat over the border.

As unlikely as it seems, the government welcomed the birders. "New Zealand is not seen as much of a threat to anyone," Riegen says, by way of explanation.

The trust has been working to find out more about the shorebird population in North Korea.

They have identified several internationally significant shorebird sites, each hosting more than 1 per cent of a given species.

"Most of the coastal strip along that western side of North Korea is farmland," he says.

"There's not a lot of chemicals used, because there's bans on importing, or the West isn't supplying fertilisers.

"It's probably the biggest organic farm in the world."

For Riegen, the importance of North Korea to the fragile flyway ecosystem isn't really acknowledged.

"It's something they should be proud of — they've actually got sites they haven't destroyed," he says. "If we get in early, before they do get enough money to destroy them, maybe we can make a difference."

In other words, Riegen says, North Korea acts as a safety valve for the entire flyway.

But North Korea is only a stopover: the final destination is further north, in the breeding grounds of the Arctic Circle.

Birds without borders

That shorebirds would fly to the remote reaches of the world — to Siberia, Alaska and Mongolia — to breed seems counterintuitive.

Yet their strategy is sound. When they arrive in spring, the winter's snow and ice are melting, forming pools of water that attract mosquitoes and other insects.

At this time of year in Siberia, mosquitoes can mass in clouds that turn the sky grey, forcing residents and researchers to wear protective clothing.

"When spring is coming, it is a spring of light and of sound," says Birds Russia CEO Dr Evgeny Syroechkovskiy.

The insects are a perfect food source for the newly arrived shorebirds, who need all the energy they can get after their long journey.

The insects also provide a perfect banquet for when the chicks hatch several weeks later, sporting short, soft bills.

Shorebirds time their arrival in the Arctic perfectly: their breeding plumage helps them blend in among the low sedge and mosses of the thaw, and they aim to hatch their eggs at the height of the insect boom.

But that boom is changing.

"Climate change is a pervasive problem that is pretty much affecting all the species on Earth," says UNSW biologist Dr Nick Murray.

"As snow is melting in the Arctic areas earlier each year, there is a timing mismatch with food resources.

"Chicks hatching from their eggs are missing the peak time of food abundance — they're growing much smaller than they otherwise would, including having a smaller bill length. That has consequences throughout the first years of their life."

"What we are seeing is that these birds are not surviving as much as they used to."

The chicks, which hatch from eggs laid directly on the ground, emerge small but fully formed.

"They weigh maybe five grams, like a little bumblebee with huge feet," says Roland Digby from the Wildfowl and Wetland trust in the UK.

"By the time they are 20 to 21 days old they are fully fledged. From 23 to 25 days old these birds start their incredible migration," Digby says.

The juveniles are not guided by adults for the first migration of their lives. They simply know the right direction, and take to the sky.

"These birds cannot land on water. They have to be incredibly sure of what they're doing," says Richard Fuller.

How exactly they do this is still something of a mystery to scientists. They may navigate by the stars and sun, but the shorebirds also have the ability to sense magnetic fields, thanks to a chemical contained in their head.

"How can they behave as if they've got a GPS on board?" marvels Theunis Piersma, professor of Global Flyway Ecology at the University of Groningen in the Netherlands.

"The birds very often seem to know exactly where they are, whether this is in a landscape with features, or over the ocean, which is a featureless landscape. Incredible."

Shorebirds also appear to be able to predict weather over the Pacific, days in advance.

They use low pressure systems like a slingshot, flinging themselves towards their destination.

Some birds, like the Alaskan bar-tailed godwits, fly directly south in one hop. Other birds stop off at the Yellow Sea before flying further south to their overwintering grounds.

The flights take up to ten days. Even with all the fat they've stored, how do they survive?

"What they can do is slow everything down, so they slow down non-essential systems, non-muscular systems that they don't need for their powered flight," says Fuller.

"They can actually shut down half of their brain at a time and essentially fall half asleep, and get sort of cognitive rest."

Despite this physiological adaptation, migration is difficult: typhoons, cyclones and even just stormy nights deplete the energy of the tiny birds. None are bigger than two kilograms, and some weigh as little as 50 grams.

Home is everywhere when you are a migratory bird. But it's hard not to imagine that they feel relief when the muddy shores of New Zealand, or Broome, or Botany Bay appear.

"Sometimes you just see a little flock of birds land and you just know that these are birds that have just literally arrived," says Adrian Riegen.

Often, the birds fall over—exhausted—as soon as they land.

Their legs have been tucked tight beneath them for over a week. Their wings are locked in position for flight. They can't hold themselves up.

But only a few hours later the waders—the snipes, the curlews, the godwits, the stilts, the stints, the knots, the turnstones—pick themselves up and start eating.

They've survived this time and they have another journey to prepare for.

They are migratory shorebirds, and it's a long way north.

Ann Jones spent six months recording the sounds of shorebirds along the whole flyway for ABC RN's Off Track, as part of a collaboration with the BBC World Service.

Listen to the series — and subscribe to the program — here.

Credits

Reporter: Ann Jones

Ann Jones Photography : Ann Jones, Dan Weller, Adrian Boyle, Adrian Riegen, Dr Nial Moores, Nigel Jackett, Ying Chi Chan

: Ann Jones, Dan Weller, Adrian Boyle, Adrian Riegen, Dr Nial Moores, Nigel Jackett, Ying Chi Chan Digital production: Alex McClintock, Tiger Webb

Alex McClintock, Tiger Webb Developer: Colin Gourlay

Colin Gourlay Designer: Ben Spraggon

Topics: science-and-technology, animal-science, climate-change, birds

First posted