What's Killing the World's Shorebirds?

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WHAT’S KILLING THE WORLD’S SHOREBIRDS? Researchers brave polar bears, mosquitoes and gull attacks in the Canadian Arctic to investigate an alarming die-off.

BY MARGARET MUNRO

our gun-toting biologists scramble out the Southern Hemisphere. They make these Although the trend is clear, the underlying of a helicopter on Southampton Island epic round-trip journeys each year, some flying causes are not. That’s because shorebirds travel in northern Canada. Warily scanning farther than the distance to the Moon over the thousands of kilometres a year, and encounter the horizon for polar bears, they set off course of their lifetimes. so many threats along the way that it is hard to Fin hip waders across the tundra that stretches The birds cannot, however, outfly the threats decipher which are the most damaging. Evi- to the ice-choked coast of Hudson Bay. along their path. Shorebird populations have dence suggests that rapidly changing climate BOOTHROYD MALKOLM Helicopter time runs at almost US$2,000 per shrunk, on average, by an estimated 70% across conditions in the Arctic are taking a toll, but hour, and the researchers have just 90 minutes North America since 1973, and the species that that is just one of many offenders. Other cul- on the ground to count shorebirds that have breed in the Arctic are among the hardest hit1. prits include coastal development, hunting in come to breed on the windswept barrens near The crashing numbers, seen in many shorebird the Caribbean and agricultural shifts in North the Arctic Circle. Travel is costly for the birds, populations around the world, have prompted America. The challenge is to identify the most too. Sandpipers, plovers and red knots have wildlife agencies and scientists to warn that, serious problems and then develop plans to flown here from the tropics and far reaches of without action, some species might go extinct. help shorebirds to bounce back.

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In chilly summer “It’s inherently massive PRISM survey is nearing completion. peak abundance of insects, so the birds do not conditions, Paul complicated — these It is a short, intense season for both the grow as big. Smith surveys the birds travel the globe, birds and the biologists. The East Bay site, When those undersized knots migrate to Arctic landscape for so it could be any- several hundred kilometres north of the tree their West African wintering grounds, they shorebirds. thing, anywhere, line, comes alive in June with the mating and run into further problems because their short along the way,” says territorial calls of a dozen shorebird species. bills cannot reach deeply buried clams, their ecologist Paul Smith, a research scientist at Among them are the robin-sized red knot, preferred food. “We show the smaller individ- Canada’s National Wildlife Research Centre in which flies up from the tip of South America; uals live shorter lives and have lower survival Ottawa who has come to Southampton Island several plovers and sandpipers; and the ruddy than larger individuals,” van Gils says. to gather clues about the ominous declines. He turnstone (Arenaria interpres) that winters in He says that he had his first close-up look at heads a leading group assessing how shorebirds Latin and South America. the knots’ Arctic breeding grounds last sum- are coping with the powerful forces altering Shorebirds stream north on four main mer, when he joined a US team to study a sub- northern ecosystems. flyways in North America and Eurasia, and species that migrates to Alaska, where chicks’ Researchers say it is now more crucial than many species are in trouble. The State of North growth rates also seem to be slowing as tem- ever to understand how conditions in the Arctic are altering breeding and survival. “This is high urgency,” says ecologist Jan van Gils of the Royal Netherlands Institute for Sea Research in Texel, “FOR KNOTS, THERE IS NO WAY OUT — who is studying the decline of wading birds called red knots (Calidris canutus) that breed in the Russian Arctic. “It’s indeed now or never.” THEY ARE ALREADY AT THE NORTHERN GUNSHOTS AND PANCAKES EDGE OF THE WORLD.” At his base camp on the island, Smith looks as if he could have walked out of a tech lab in Silicon Valley — except for the shotgun America’s Birds 2016 report1, released jointly by peratures climb. The data collected last year slung over his shoulder. He is constantly in wildlife agencies in the United States, Canada are still being analysed, but van Gils suspects motion, up before 7 a.m. and in the helicop- and Mexico, charts the massive drop in shore- another timing mismatch there — chicks miss ter by 9, ready to head north to survey shorebird populations over the past 40 years. the peak insect emergence. birds. At 6 p.m., he’s in the kitchen cabin, The East Asian–Australasian Flyway, where Conditions are also changing rapidly at humming away as he cooks dinner for the shorelines and wetlands have been hit hard by Smith’s research site in Canada, where sea ice hungry crew returning from their nest hunts. development, has even more threatened spe- last year broke up more than a month ear- He deals with a computer glitch before bed, cies. The spoon-billed sandpiper (Calidris lier3 than it did three decades ago. But when and then scrambles out of his sleeping bag at pygmaea) is so “critically endangered” that it comes to the shorebird population declines 2 a.m. when a curious polar bear wanders into there may be just a few hundred left, accord- at East Bay, says Smith, “there may be more camp. He deters it with several warning shots, ing to the International Union for Conserva- immediate threats than climate change”. which makes for animated conversation over tion of Nature. Snow geese (Chen caerulescens) are high on the pancakes that he whips up later that morn- Red knots are of major concern on several his list of suspects. The goose population has ing. Then, he hikes off to set contaminant col- continents. The subspecies that breeds in exploded in North America, and they have lectors in thigh-deep melt ponds to check for the Canadian Arctic, the rufa red knot, has severely degraded wetlands along the coast of pollution that might be affecting the birds. experienced a 75% decline in numbers since Hudson Bay that serve as key refuelling stops Smith has been coming to this site, known the 1980s, and is now listed as endangered in for millions of migrating shorebirds4. as East Bay, every year since 2000, when he was Canada. “The red knot gives me that uncom- Geese are also showing up in shorebird sent here as a biology student to help build a fortable feeling,” says Rausch, a shorebird breeding territory, where they mow down the camp to study poorly understood shorebirds. biologist with the Canadian Wildlife Service grasses that the shorebirds use to protect their He was soon intrigued by the birds — some no in Yellowknife. She has yet to find a single rufa- nests on the wide-open landscape. Perhaps bigger than a sparrow — that fly across conti- red-knot nest, despite spending four summers even more threatening, says Smith, is that the nents to lay eggs on the wide-open landscape. surveying what has long been considered the geese attract foxes and other predators that eat Sleet is not uncommon in June, cold winds bird’s prime breeding habitat. shorebird eggs and chicks. blow in off Hudson Bay in July and snowdrifts The main problem for the rufa red knots is Southampton Island is an ideal spot for can persist well into August. thought to lie more than 3,000 kilometres to gauging the impact because there are now about Smith now heads studies at the 12-square- the south. During their migration from South 1 million nesting snow geese on the island. A kilometre research plot at East Bay, one of the America, the birds stop to feed on energy- sister research site that Smith runs on nearby longest-running shorebird-research camps rich eggs laid by horseshoe crabs (Limulus Coats Island — less than an hour away by Twin in the Arctic. He is also co-leader of a joint polyphemus) in Delaware Bay (see ‘Tracking Otter aircraft — provides a control because the effort between Canada and the United States trouble in the Arctic’). Research suggests that island does not have a snow-goose colony. called the Arctic Program for Regional and the crabs have been so overharvested that the International Shorebird Monitoring (Arc- red knots have become deprived of much- HIDDEN NESTS tic PRISM). The project, which began in needed fuel. One day in late June, biologist Lisa Kennedy 2002, has dispatched crews to more than In other cases, climate change might be the calls out a warning as she surveys the East Bay 2,000 sites, stretching from Alaska to Baffin prime problem. Van Gils’ team in the Nether- research site. “Careful where you step,” says Island in eastern Canada, to survey the 26 lands has found that red knots that breed in the Kennedy, sticking to the larger rocks for fear shorebird species that breed in the North Russian Arctic produce smaller offspring dur- of crushing the speckled eggs of a plover. A American Arctic. Smith and his Canadian ing summers when the snow melts early2. He doctoral student at Trent University in Peter- co-leader, Jennie Rausch, cover the central suspects the reason to be malnutrition. During borough, Canada, Kennedy led the six-person and eastern Arctic, and the first round of the warm years, the red-knot chicks may miss the crew that combed for nests last summer.

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! STOLEN ARCTIC EGGS SNOW GEESE Less than 7% of the shorebird eggs at Prince Charles East Bay on Southampton Island Island The population of snow Red knot geese (Chen caerulescens) hatched successfully, whereas the rate and other geese in the at Coats Island topped 55%. The North American Arctic has di erence? Coats Island has no snow Southampton surged from about geese but East Bay is overrun. When ! Island 1.5 million in the 1960s to shorebirds leave their nests to defend East against encroaching geese, that HYDROELECTRIC DAMS as many as 20 million Bay today because of changes provides an opportunity for predators Red knots wearing trackers to US farming that provide to steal eggs. revealed a previously unknown abundant food sources for EAST BAY stopover site during their the birds. northward migration near 20/296 eggs hatched hydroelectric dams along the Coats Nelson River on the west coast Island of Hudson Bay. Researchers Tracking have raised concern that the Hudson dams can change water ow Bay and temperatures in ways that might harm the birds.

Nelson trouble in River Southern Deltadelta James Bay COATS ISLAND Fraser 247/448 eggs hatched the Arctic River delta CANADA Migrating shorebirds face a long list of hazards Spy tech on their epic ﬂights. Trials MOTUS NANOTAG and trails Pearl-sized nanotags (shown here BY MARGARET MUNRO and on back of bird), that weigh as The red knot has a wingspan of AND RICHARD MONASTERSKY little as 0.25 grams are so light that about 50 centimetres, but it makes Delaware All tags shown they can be glued onto small birds, one of the longest animal Bay DESIGN BY JASIEK KRZYSZTOFIAK bats and insects. Batteries can last a actual size migrations known, from the tip of ! NEGATIVE NUMBERS XT4 couple of weeks to a year, powering South America to the Arctic. The ID tag coded transmissions that get picked rufa subspecies, which breeds in HORSESHOE-CRAB Since the 1970s, migratory shorebird up by a network of towers. Nanotags northern Canada, has been hard HARVEST species have experienced a 70% drop any shorebird populations are declining UNITED in population size, on average. fall o when birds moult. COOPER EMILY BIRD ILLUSTRATION: hit in recent decades and is listed Red knots time their steeply around the globe, and those that nest as threatened by the United States migration north to refuel on and endangered by Canada. STATES eggs laid by horseshoe 1975 in the Arctic are among the hardest hit. On SATELLITE TAG crabs in Delaware Bay. their long-distance migrations, they encounter Tags attached to backs of birds Overharvesting of the crabs M send or receive signals from is thought to have a number of threats, including hurricanes and satellite networks to track the contributed to the steep 1980 hunters, pesticides in croplands and human sprawl location of the birds as they decline of the birds. that is destroying wetlands used by the birds as migrate. These tags are bigger than Motus nanotags and geolocators refuelling stations. By tracking the journeys of each and are worn until they can be species, researchers can better understand the removed from the bird, or fall o . 1985 problems confronting these birds. GEOLOCATOR MEXICO Gulf of Mexico Shorebirds are vulnerable because their DOMINICAN Long-lasting tags, typically attached REPUBLIC 1990 migrations are tightly tuned to the cycles of CUBA to the leg, record sunrise and sunset, other species. The robin-sized red knot (Calidris which can be used to establish PUERTO canutus, pictured) that breeds in the Canadian rough estimates of a bird's latitude RICO HAITI and longitude. Tags must be 1995 Arctic times its northward migration so that it can recovered to retrieve data. stop and bulk up on the eggs of horseshoe crabs JAMAICA To east coast of (Limulus polyphemus) in Delaware Bay. Western Caribbean Sea BELIZE South America sandpipers (Calidris mauri) touch down every spring Animal 2000 GUATEMALA ! on Canada’s west coast to feast on biofilm produced network MAP KEY HONDURAS by algae along the expansive mudflats of the Fraser 15-km HUNTING A powerful new tool in animal Motus towers Hunting is a threat to River delta. And all the Arctic breeders aim to have range ! Threats EL SALVADOR NICARAGUA 2005 research is the Motus Wildlife Active shorebirds, particularly in their chicks hatch at a time when there is a banquet Tracking System, which uses a Inactive, temporary Snow-goose several Caribbean islands network of towers that capture of mosquitoes and other insects on the tundra. Tracking or seasonal stations population range COSTA RICA and northern South signals from nanotags. The system tower America. E orts are But there is growing concern — and evidence — has some 300 towers located PANAMA 2010 Flight paths Nelson River currently under way to mostly in North America, and is that the connections have begun to fray because recorded 2014–15 hydroelectric plants better estimate the annual expanding to other continents. harvest, with an aim of of climate change and other human impacts on Person Spring Existing for scale preventing the loss of too 100 50 0 50 100% the environment and ecosystems. Autumn Planned many birds. Average population change

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le c ir C c ti Population rc A problems

migrate. These tags are bigger than Motus nanotags and geolocators and are worn until they can be removed from the bird, or fall o . 1985

GEOLOCATOR MEXICO Gulf of Mexico DOMINICAN Long-lasting tags, typically attached REPUBLIC 1990 CUBA to the leg, record sunrise and sunset, which can be used to establish PUERTO rough estimates of a bird's latitude RICO HAITI and longitude. Tags must be 1995 recovered to retrieve data. JAMAICA To east coast of Caribbean Sea BELIZE South America Animal 2000 GUATEMALA ! network MAP KEY HONDURAS 15-km HUNTING A powerful new tool in animal Motus towers range ! Threats EL SALVADOR NICARAGUA Hunting is a threat to 2005 research is the Motus Wildlife Active shorebirds, particularly in Tracking System, which uses a Inactive, temporary Snow-goose several Caribbean islands network of towers that capture Tracking or seasonal stations population range COSTA RICA and northern South signals from nanotags. The system tower America. E orts are has some 300 towers located PANAMA 2010 Flight paths Nelson River currently under way to mostly in North America, and is recorded 2014–15 hydroelectric plants better estimate the annual expanding to other continents. harvest, with an aim of Person Spring Existing preventing the loss of too 100 50 0 50 100% MOTUS TOWERS, STUART MACKENZIE; BIRD FLIGHT PATHS, SJOERD DUIJNS; STOLEN-EGG DATA, PAUL SMITH PAUL DATA, SJOERD DUIJNS; STOLEN-EGG BIRD FLIGHT PATHS, MACKENZIE; STUART TOWERS, MOTUS for scale 4; REF. 1; GOOSE POPULATION, SMITH & REF. ADAM DATA, POPULATION-DECLINE SOURCES: Autumn Planned many birds. Average population change

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The young biologists instantly identify birds by their silhouettes, calls and behaviour. They are also quick to spot polar bears that can appear seemingly from nowhere, which is why shotguns are taken everywhere — even to the outhouse. The biologists hike 10–15 kilometres a day across the tundra and melt ponds to find and monitor nests. They also spend a lot of time lying motionless on the soggy ground waiting for shorebirds that they spooked to return to their eggs. It can sometimes take days to locate the well-hidden nests — some are circular cups the birds dig in the ground; others just grass, moss and the odd feather pulled together. The researchers weigh and measure the birds and their eggs and put the nests under surveillance. They also fit many birds with bling — bands around the legs and pearl- sized nanotags that are glued to their feathery backsides. “You have to be careful not to stick Dunlins (Calidris alpina) are among 14 shorebird species that regularly breed on Southampton Island. yourself to the bird,” says Kennedy, holding a nanotag in place on a semipalmated plover on Southampton Island has dropped so low to develop the most efficient conservation until the Krazy Glue sets. that the population can no longer sustain itself. actions. “But it’s a data-hungry system,” says Then the bird is off, the hair-like anten- The research adds to long-standing con- Andres. “So until we have the sources of infor- nae on the tag emitting an electronic pulse cerns about North America’s goose explosion. mation, it is hard to do.” that can be picked up by the receiving station The geese used to winter in the coastal marshes Van Gils also stresses the need to find the on top of a cabin back at camp. This is part of of Louisiana and Texas, but now spend the sea- mechanisms driving the declines, which he BOOTHROYD MALKOLM the Motus tracking system, a network of some son feasting on leftover crops on farm fields expects to worsen, given the unrivalled warm- 300 receiving towers that is expanding across the in the southern and Midwest United States. In ing rates seen in the Arctic. “For knots, there is Americas. The Motus nanotags weigh less than the spring, the geese fly to the Arctic to breed. no way out — they are already at the northern 0.3 grams — so light that they can be carried by Robert Rockwell, a population biologist and edge of the world,” says van Gils, who predicts the smallest shorebirds and their chicks. Their ecologist at the American Museum of Natural that many knot subspecies will collapse over signals are picked up when the birds are within History in New York City, says that it has been the next 50 years because of warming and 15 kilometres of a receiving station. “pretty staggering” to watch the goose popula- trophic mismatches. On his computer, Smith has watched red tion explode from 1.5 million in the 1960s to For now, the shorebirds are back in the knots make the 3,000-odd-kilometre flight to what he estimates could be as many as 20 mil- sunny southern climes, settled onto beaches the Arctic from Delaware Bay on the US coast lion today. He has run a decades-long moni- and wetlands often shared with tourists, in three days. “They go ‘ding, ding, ding’ as toring project on La Pérouse Bay on the coast shrimp farmers and hunters. Rausch and they hit the towers,” he says. of Hudson Bay, where he and his colleagues Smith have hung up their waders and are back Shorebirds make some of the longest migra- first showed5 how geese can rip up lush green at their desks, drawing up plans for the camps tions in the animal kingdom. One red knot, grass and marshland and render it inhospita- and aircraft that they’ll use to catch up with the sporting leg band B95, journeyed to and from ble to both plants and animal species such as shorebirds in the Arctic again next June. the southern tip of South America and the shorebirds. Subsequent work6 has shown that One priority is to send a nest-hunting crew Arctic for more than 20 years. geese have triggered long-term damage that to Prince Charles Island in northwestern Hud- The nanotags that Smith’s group uses in the has reduced the biodiversity of plants, insects son Bay, which was alive with shorebirds when Arctic are helping to fill in details about the and birds at several other sites. it was last surveyed in the 1990s. Rausch and ultramarathon migrations. In 2014, Smith and Whether geese have enough of an effect to Smith flew there to scope out locations for a his colleagues discovered that red knots were be a major factor in the shorebird declines is research camp in late July, and as their plane stopping to refuel at a previously unknown still unclear. Rockwell says that the question of came in to land, they spotted one species they spot along the coast of Hudson Bay. goose impacts is a crucial issue, and applauds had hoped not to see, says Smith: “The island Nanotags are also valuable on the breeding Smith’s team for trying to answer it. was covered with breeding geese.” ■ grounds because they enable Smith’s team to monitor how much time adults spend on their FIGHT FOR FLIGHT Margaret Munro is a freelance journalist in nests, and how far hatchlings wander in search Brad Andres, national shorebird coordina- Vancouver, Canada. of insects — two of many variables affected by tor of the shorebird conservation plan for the geese. Nesting shorebirds will take flight to US Fish and Wildlife Service in Falls Church, 1. North American Bird Conservation Initiative. The State of North America’s Birds 2016 (Environment defend their nests from grazing geese, leaving Virginia, says that there is a huge need to and Climate Change Canada, 2016). their eggs and chicks vulnerable to the foxes understand how different threats and distur- 2. van Gils, J. A. et al. Science 352, 819–821 (2016). and predatory birds. bances impact shorebird survival — be it snow 3. Canadian Ice Service. North American Arctic Waters Spring 2016 (Environment and Climate Change This year, predators took most of the shore- geese in Arctic Canada, insect abundance in Canada, 2016). bird eggs laid on the East Bay research plot. Alaska and Russia or the destruction of feeding 4. Flemming, S. A., Calvert, A., Nol, E. & Smith, P. A. Just 20 eggs out of 296 survived long enough grounds and refuelling stops caused by coastal Environ. Rev. 24, 393–402 (2016). 5. Abraham, K. F. et al. Arctic Antarctic Alpine Res. 37, to hatch. At the snow-goose-free site on Coats development in the tropics and midlatitudes. 269–275 (2005). Island, more than half the eggs hatched. Smith Researchers are building models to pin- 6. Koons, D. N., Rockwell, R. F. & Aubry, L. M. J. Anim. says that the reproductive success of shorebirds point the biggest dangers and help managers Ecol. 83, 365–374 (2014).

20 | NATURE | VOL 541 | 5 JANUARY© 22017017 M a|c CORRECTEDmillan Publishers L i6m iJANUARYted, part of Sp r2017i nger Nature. All ri ghts reserved. ©2017 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. CORRECTIONS The News Feature ‘What’s killing the world’s shorebirds’ (Nature 541, 16–17; 2017) misidentified a picture of a dunlin (Calidris alpina) as a red knot (Calidris canutus).