The last two captive Spoon-billed Sandpipers passed away one after another, and an artificial breeding process spanning 13 years failed to retain them

The last two Spoon-billed Sandpipers at Slimbridge Wetland Center were just one day away from dying. The staff considered what to do when the last one was left. Should he look for a few other species of snipe to keep him company? Which species is more suitable to choose, and how can we help them get along well with each other? On the day when the penultimate bird died, while others were busy with the autopsy, someone noticed that the remaining Spoon-billed Sandpiper showed obvious behavioral changes. Not only did its calls increase, but it also always stood guard at the door of the aviary, as if looking for the whereabouts of its companions.

The next day, it died too. This is November 11, 2024. The crowds wearing poppies on the streets to commemorate the ceasefire of World War I did not know that a longer battle also came to an end on this day.

Meet the Spoon-billed Sandpiper

The spoon-billed sandpiper (Calidris pygmaea) is a small waterbird about the size of a sparrow. Its most obvious feature is that the end of its long black beak is swollen, resembling a small spoon. Birdwatchers also nickname it "spoon". It will walk forward on the shallow tidal flats of the wetland, while lowering its head and paddling left and right with this small spoon to pick up moss and small insects and eat them. It is very cute.

Spoon-billed Sandpiper. Gallery copyright pictures, reprinting and using may cause copyright disputes

But its life history has a grandeur that doesn't match its petite size.

Many birds breed in high latitudes in summer and spend the winter at low latitudes. The Spoon-billed Sandpiper's breeding grounds are in Kamchatka and the Chukotka Peninsula in northeastern Russia, while its wintering grounds are along the coast of Southeast Asia. The two places are more than 8,000 kilometers apart. In order to span this long journey, it needs to stop briefly in various wetlands in China, Japan, South Korea and other places to replenish energy before continuing on the road. This route forms the core of the East Asian-Australasian Flyway, along which 50 million waterbirds make their annual journey. This is one of the greatest migrations on the planet, but it is also one of the most critical.

Population density and land pressure in East Asia are already among the highest in the world, and whenever land development and transformation occurs, wetlands are always the first to suffer. The Tiaozini Wetland in Yancheng, Jiangsu Province is one of the largest and most important supply stations in the migration area. However, as late as 2011, Yancheng also launched a one-million-acre tidal flat reclamation plan, and 346,000 acres of the 400,000 acres of Tiaozini wetland were included in it. By the time the project was suspended, more than 100,000 acres had been converted into marine aquaculture farms.

Every wetland destroyed will affect all migrating birds along the way, resulting in a compound superposition of harm. The number of adult Spoon-billed Sandpipers was estimated to be nearly 6,000 in 1977, but had dropped to 2,000 in 2002, and to less than 500 in 2010. It is listed as "critically endangered" on the International Union for Conservation of Nature's Red List, and is only one step away from extinction. Following this trend, people fear that Spoon-billed Sandpipers will disappear from the earth by 2020.

According to common sense, the first option to save endangered animals is to set up protected areas so that their living environment will no longer be disturbed by humans. However, protecting migratory birds requires the cooperation of every country and region along the way, and no problems can occur in any link; in the face of imminent extinction, no one has such confidence. What's more, the migration route of the Spoon-billed Sandpiper is still not fully understood, and there are many hidden breeding grounds, wintering grounds, and transit grounds that may disappear forever before researchers can find them.

So the researchers launched a project with an uncertain future: ex-situ conservation of Spoon-billed Sandpipers: moving a small group of birds to a safe environment to raise them in captivity. In 2011, the year the Million Tidal Flat Reclamation Project began, a research team led by the Wild Bird and Wetland Foundation went to Plum Village in Chukotka State, Russia, where they collected 25 Spoon-billed Sandpiper eggs, hoping to allow them to grow and breed in a completely artificial environment to establish a backup population.

The captive location was chosen in the village of Slimbridge in Gloucestershire, England. The name of the village means "narrow bridge". The foundation has a conservation center here, which was established in 1946 by Sir Peter Scott, the only son of explorer Robert Scott, who died in Antarctica.

Difficulties in ex-situ conservation

Everyone involved knows how difficult this project is.

The Spoon-billed Sandpiper's annual migration of eight thousand kilometers means the actual season they experience is very special. From October to April every year, Spoon-billed Sandpipers wintering in Southeast Asia experience high temperatures that often exceed 30 degrees Celsius and lows around 20 degrees Celsius. On the contrary, when Spoon-billed Sandpipers return to their breeding grounds in Russia every July, the maximum temperature is only 15 degrees, and the lows can be around 0 degrees. It is cool in the middle of the year and hot at the end of the year, almost the opposite of the British climate. Most areas of the aviary are only isolated from the outside world by nets, making it difficult to control the temperature. Although Spoon-billed Sandpipers can be temporarily locked in a heated room during the severe winter, summer is their breeding season, and if their movements are restricted, they will not be able to reproduce normally.

However, we cannot simply reverse winter and summer. This is not only because the Spoon-billed Sandpiper has its own development progress, but also because the physiological activities of the Spoon-billed Sandpiper also require photoperiod. The pattern of long days in summer and short days in winter has not changed due to its migration. Although artificial light can be used when there is insufficient light, it will be difficult to save if there is too much light.

Although there was sufficient psychological preparation, the actual difficulties encountered were beyond everyone's imagination. The curved transparent roof of the aviary causes heat to accumulate in summer, and the isolation of different areas hinders ventilation. The summer heat makes Spoon-billed Sandpipers listless and sleepy, which delays a lot of breeding time. The coldness of winter has caused the time of shedding to be misaligned, and a small amount of winter hair has continued into the summer. The staff devised various remedies, including placing ice cubes, adding ventilation fans, constantly changing water, and burying floor heating in the soil.

There was also a problem with the lighting. At first, the fill light was a low-frequency fluorescent lamp. Later, I realized that the flickering of the lamp might have adverse consequences, so I changed it to a high-frequency one. Birds can sense ultraviolet light that is invisible to the human eye, and ultraviolet lights were installed in the facility, but no one carefully measured the actual brightness.

Image source: WWT

In 2016, the first batch of Spoon-billed Sandpipers successfully bred in complete captivity and without migration, laying seven eggs. However, the researchers' excitement was quickly dampened. Only 2 of the 7 eggs hatched successfully, and the two chicks died soon after. The inspection revealed that this batch of eggs had a very serious calcium deficiency problem. The eggshells of one nest of eggs were extremely thin and the cuticle was missing. One of the eggs was even soft and collapsed soon after. As for the two dead birds, autopsies revealed severely low bone density. In addition, the physical condition of many female birds significantly declines during the breeding season, which may be caused by using their own calcium reserves to fill the gap. After that, the staff set up new UV lights, added vitamin D to the feed, and added some rat tails because new research found that wild polar birds eat lemming bones and teeth to get their calcium.

As of 2021, a total of 19 eggs have been laid by captive Spoon-billed Sandpipers. Seven chicks hatched, three of which lived to the age of flight. However, the project came to an end here, because in this year, the last female bird died, and only the male birds were left in the flock.

The survival crisis of captive Spoon-billed Sandpipers

Spoon-billed Sandpipers in captivity suffer from various injuries and illnesses. The inadaptation to temperature and light puts tremendous stress on their physiology, and some remedies make the situation worse. In 2019, staff tried to change the photoperiod to trick Spoon-billed Sandpipers into entering the breeding season earlier, so that their breeding could be staggered during the hot British summer. Although the plan was successful, a widespread Candida infection broke out in the flock, and four birds died in just two months. Researchers speculate that this may be caused by disrupted rhythms. Amyloidosis and chronic plantar dermatitis are also recurring causes of death.

But the most distressing thing is the death caused by an in-flight collision. The aviary at Slimbridge was good by conservation center standards, but no aviary could compare to the vast tundra of Siberia. Netting was installed on the ceiling of the aviary and around the light fixtures to provide a little cushioning for the impact. However, it was later discovered that the netting was too elastic and would bounce the tiny Spoon-billed Sandpiper back to the ground like a trampoline. Despite repeated remediation, strikes resulted in the death of 10% of the birds.

Some injuries from flight impacts (spinal injuries, eye injuries, beak injuries). Image source: WWT

In fact, the Spoon-billed Sandpiper can learn to perform limited flights in a small space, but once an accident occurs or a fright occurs, it cannot take care of it. Sometimes such frightening is caused by the presence or cry of raptors nearby, and sometimes the reason is unknown. In 2018, the first bird that successfully grew up here suddenly flew away on the night of the 49th day and was killed.

After that, the researchers had to clip the flight feathers of all the chicks. They hope that by the time the young birds moult and grow new flight feathers, they will have adapted to the environment of the aviary, just as their parents have adapted to not using flight displays to court mates. But what kind of impression will a little bird that grows up like this leave on its own small world?

new hope

The last two eggs of 2021 are in poor condition. When Egg No. 1 was discovered, there were already dents in the shell. The staff used glue to seal the cracks, applied nail polish, and wrapped them in plastic wrap to prevent the egg from losing water. However, the bangs still sunk deeper and deeper, and they gave up on the 18th day. Egg No. 2 had a normal appearance, but no trace of blood vessels could be seen through light transmission. It had no movement and no structure. It was given up on the 24th day. This is probably due to the poor physical condition of the female bird. The female died two months later, and Slimbridge's artificial breeding project failed.

Although there are still a few male birds left in the center, it is no longer possible to release them into the wild. They have never experienced true migration and are likely to be unable to survive in the wild. Therefore, the center's mission shifted to scientific research and education, and it began to receive limited visits from outsiders. In 2024, when the last one dies, the project will finally be completely completed.

But the Spoon-billed Sandpiper’s story doesn’t end here. The failure of the relocation project provided valuable lessons for other conservation methods. Although Slimbridge suffered repeated setbacks in his pursuit of population reproduction, he proved that healthy eggs are very tenacious and can grow successfully under artificial conditions. Inspired by this, when researchers collected the second batch of eggs for the relocation project in Meicun in 2012, they also launched a parallel project, which was to take the Spoon-billed Sandpiper eggs, artificially hatch them nearby, and then return them to the flock. This not only improves the survival rate of eggs, but also encourages the mother bird to lay more eggs each breeding season. This project has achieved outstanding results, increasing the breeding success rate of Spoon-billed Sandpipers by 4 times, and has now become the main means of breeding colony conservation.

Meanwhile, other projects and collaborations to protect Spoon-billed Sandpipers are also progressing. In 2008, China joined the East Asian-Australasian Flyway Partnership Agreement. In 2016, the State Council issued the "Wetland Protection and Restoration System Plan" and set a wetland red line of 800 million acres. In 2019, Yancheng Tiaozini Wetland was listed as a World Natural Heritage as part of the Yellow and Bohai Sea migratory bird habitat. In January 2025, a simultaneous survey of Spoon-billed Sandpipers overwintering in China found 75 individuals, breaking the historical record. According to estimates in 2024, there are approximately 331 to 554 adult Spoon-billed Sandpipers. The population is still declining at a rate of 5% per year, but compared with the 26% rate in previous years, people have already seen a glimmer of hope.

thoughts of protection

Slimbridge's Spoon-billed Sandpipers may not know why they spread their wings, but they retain this instinct. During the migration seasons of spring and autumn every year, captive Spoon-billed Sandpipers will become obviously restless, increase their activity, and run around and circle in the aviary. The staff designated a special breeding area in the aviary and used recipes, vegetation, and photoperiod to simulate changes in the environment. However, what kind of simulation is needed to reproduce the flight itself?

Although it sounds like nonsense, every living thing on the earth has evolved on the earth. Whether it is the history of a species or the life of an individual, it is all saturated with the earth, ocean and sky of this planet. The environment will change, and organisms can change accordingly, but the speed of change is limited. If you were suddenly cut off from the world, you might be able to survive, but you wouldn't be able to thrive.

This is a dilemma that every ex-situ conservation project faces. Indeed, if wild populations collapse completely, captive populations are the last hope. But this hope is so broken and so poor. The Spoon-billed Sandpipers of Slimbridge may eventually forget the wilderness of Chukotka, the tidal flats of Yancheng, the islands of Bangladesh and the salt pans of Thailand, but in what kind of world will we think this is a good thing?

At this moment, we are still at a fork in the road. This fork in the road will determine the fate of the spoon-billed sandpiper, the survival of the East Asian-Australasian Flyway, and the face of our planet. Indeed, no matter what kind of environmental disaster we encounter, human beings will not be easily extinct. The genetic information of species can also be preserved. It is even possible to build an ark so that every creature can occupy its place in flesh and blood. However, this interception is just a fragment of life. Even if one day all the destroyed habitats are restored, the population cannot pretend that nothing happened and start over. What awaits them is long and painful reconstruction.

And then, we will live on an earth that has lost its color.

One phenomenon was documented in the project's final report. It was already winter when the first Spoon-billed Sandpipers arrived at Slimbridge, so they were all housed indoors with heating. But all the birds were huddled in the far southwest corner of the room, not near the heat source.

That's where they're supposed to be flying this season.