Conservationists from around the world are warning huge numbers of migratory shorebirds could starve without human intervention in China, and they're planning a food drop to help.

One of the coldest winters in decades in a nature reserve in eastern China has wiped out the clam population, the major food source for the critically endangered Great Knot.

The International Union for Conservation of Nature list the Great Knot as endangered, while the Australian Government considers it to be critically endangered.

A fundraising drive is underway to pay for half a million dollar's worth of farmed shellfish to feed the birds during their long flight north.

For the past few days coastal shorebird ecologist David Melville from the Pukorokoro Miranda Shorebird Centre has been watching hungry the birds arrive in China from Australia.

He said they were flying in and looking for food that was not there.

"Drastic problems call for drastic measures," he said.

His proposal is to leave supplementary food on the tidal flat for the birds.

"We're trying to put out 500 tonnes of small clams over a period of four to six weeks," Mr Melville said.

Birds like the Eastern Curlew can travel up to 12,000 kilometres in one trip to and from places like Siberia or Alaska. ( Supplied: Dan Weller )

He said by their calculations that would provide sufficient food for the Great Knots over the period of time when they need to fatten up for their next stage of migration.

That next stage takes them from Siberia to the alpine mountain tops.

So far fundraising has raised enough money to feed the birds for about three weeks.

But Mr Melville said they needed the equivalent of $250,000 more to cover the three weeks after that.

'It's time for intervention'

Mr Melville said he hoped to start spreading the shellfish by boat next week.

"The area is already used for clam farming. So it's not a pristine natural area, it's an actively managed and farmed tidal flat," he said.

"We're really just doing what the local fishermen do.

"They haven't been able to source commercial clams to put out because the cold weather seems to have had an impact on a large area of the country."

He conceded the scheme was interfering with nature, but he said the Great Knot needed all the help it could get.

"If we didn't put the food out the birds would be out on the mud flats and probably end up starving to death," he said.

Mr Melville said the birds population was in decline and had already take a big hit in 2006, when a major site in South Korea was destroyed through reclamation.

The eastern curlew and other birds need places to feed and rest on the way, and the Yellow Sea was a crucial stopover. ( Nigel Jackett )

"We have a choice, yes we could let nature take its course and we could watch a critically endangered species get even more critically endangered," he said.

"Or we could choose to intervene for what hopefully will be a one-off event and put supplementary feed out this year to tide over part of the population so they can migrate and breed successfully."

Effect of losing a 'crucial stopover'

This is just the latest in a string of threats to the survival of many migratory shorebird species.

The birds can travel up to 12,000 kilometres in one trip to and from places like Siberia or Alaska.

Every summer Australia hosts tens of thousands of the birds, who use the time to fatten up before making their return journey.

65 per cent of the shorebird feeding grounds have been lost to development in the region since the 1960s. ( Supplied: Ann Jones )

But the birds need places to feed and rest on the way, and the Yellow Sea was a crucial stopover.

Connie Lee, from the conservation group Birdlife Australia, said about 65 per cent of the shorebird feeding grounds have been lost to development in the region since the 1960s.

"So these places that these birds stop at are becoming smaller and smaller and there's less and less space and less food," she said.

"And because they've used up all their energy stores by the time they reach the Yellow Sea, they're in no state to fly further if they have to.

"So we're seeing many birds that aren't making it the full length of their migration whether it's north or south."

A shift in attitude

But conservationists and scientists are celebrating a shift towards habitat protection in South Korea, China and Japan.

Ms Lee has been working with local authorities in South Korea to protect the Geum Estuary.

It is an important feeding ground for the critically endangered Eastern Curlew and the world's most endangered shorebird, the Spoonbilled Sandpiper.

Grey plovers take flight at Geum Estuary, North Korea. ( Supplied: Chris Purnell )

One of the last untouched feeding grounds in the region, it neighbours what was a crucial stop over for the Great Knots, until a major sea wall was built.

"This was the most important staging site for migratory shorebirds in South Korea and about 10 or so years ago they built the largest sea wall in the world," Ms Lee said.

"And so this site that had hundreds of thousands of birds visiting suddenly had no food for birds because they did a land reclamation and dried out a huge part of the mudflats.

"So in that one event we lost a quarter of the world's population of the Great Knot, so 90,000 essentially disappeared and most likely died."

Ms Lee said after years of catastrophic habitat loss, momentum was building to provide protection for migratory shore birds in the region.

"It's really exciting to see a lot more enthusiasm in these parts of the world in terms of protecting these species," she said.

Hope on the horizon

An eastern curlew at Roebuck Bay. ( Nigel Jackett )

In January this year China announced it would dramatically curb reclamation of wetlands for commercial development.

After years of bad news the University of Queensland's Professor Richard Fuller said that announcement had given him hope for the birds' future.

"It's the best news I've had as a researcher working on these migratory birds in the past 10 years," he said.

"The reason I'm so excited is because it felt like the loss of these habitats was inevitable and would just continue until there was nothing left.

"This decision alone is likely to prevent the extinctions of at least two birds species in the next decade or so.

"And I'm so pleased there's been some positive movement in a story that's been so negative for so long."

The Nordmann's greenshank population has shrunk to a few hundred. ( Ann Jones )

Those two species are the Spoonbilled Sandpiper, whose population has shrunk to a few hundred, and the Nordmann's greenshank that follows a similar flight path.

Professor Fuller said a string of World Heritage nominations would make a big difference to the most vulnerable of the species.

He said he hoped it was a sign of more positive steps to come.

"China has put forward 14 locations for World Heritage listing and they're currently working out boundaries and Korea is also preparing World Heritage nominations as well," he said.

"So it's wonderful to see this joined up conservation around the Yellow Sea."