Scientists and conservationists team up to protect imperiled migratory shorebirds
A young American oystercatcher snatches food from an adult on a Long Island beach. In the late 1800s, five to ten times more of these handsome birds foraged along Atlantic shores.
THE DAWN SKY OVER GEORGIA'S ALTAMAHA RIVER is pale pink, with mackerel clouds that seem to mirror the rippling water. Tim Keyes, a wildlife biologist with the Georgia Department of Natural Resources, pilots a fishing skiff downstream, headed for barrier islands that mark where the river meets the Atlantic Ocean. The boat rounds a curve, Keyes eases up on the throttle, and there, clustered on a non-descript sandbar, are the birds he’s come to count: American oystercatchers. There’s no mistaking their bold white-and-dark plumage, bright yellow eyes and long, improbably thick red bills.
Keyes cuts the engine, and the skiff nudges the sand a few hundred feet from the flock. He climbs out slowly, then sets up a spotting scope and starts scanning. “One hundred eighty-six oystercatchers at first count,” he says. “That’s a gorgeous sight!” With the eastern segment of this species estimated at just 11,000 birds—five to ten times smaller than scientists believe it was in the late 1800s—the flock represents a significant share of the entire population.
The American oystercatcher is one of the world’s more than 200 species of shorebirds and one of 52 species that breed in North America. Most shorebirds are long-legged, long-billed and found near water, wading or probing the sand for invertebrate prey—a behavior that led nature photographer Arthur Morris to dub the birds “beautiful beachcombers.”
Masters of migration, shorebirds also are known as “wind birds.” Many species fly surprisingly long distances between their breeding and wintering grounds, traversing countries, continents and even entire oceans. (One bar-tailed godwit outfitted with a satellite transmitter flew 7,145 miles from Alaska to New Zealand without stopping for food or water—a feat biologists compared to a human running at top speed nonstop for seven days.) Robin-sized red knots fly the farthest of all: Every year, members of the species’ Calidris canutus rufa subspecies travel some 9,300 miles each way between their southern South American wintering grounds and the Canadian Arctic, where they breed.
“Much the way humans travel long distances on highways dotted with rest stops for refueling, shorebirds migrate along ‘highways in the sky’ called flyways,” says Taj Schottland, coastal adaptation specialist for the National Wildlife Federation. When the birds stop to rest and feed at stopover sites along these routes, they can gather in staggeringly large numbers. On the East Coast, Delaware Bay is famous for attracting hundreds of thousands of shorebirds each spring, while across the continent, Alaska’s Copper River Delta hosts the largest shorebird gathering in the Western Hemisphere, about 5 million birds.
“To see a vast flock of these birds rising from the sand to wheel across the sky in unison is one of nature’s most inspiring sights,” says Schottland, who works with NWF state affiliates on the East Coast to protect and restore critical stopover sites along the region’s Atlantic Flyway.
These marathon migrations that inspire our sense of wonder also make shorebirds especially vulnerable. Birds on the move face multiple threats during the course of the year, with different dangers confronting them on breeding grounds, wintering grounds, each stop along their migratory routes and even while in flight. “The loss or degradation of just one or two stopover sites, for example, can profoundly affect a bird’s ability to survive its migratory journey,” Schottland says.
Many shorebird species indeed are in trouble. According to The State of North America’s Birds 2016, a report by the North American Bird Conservation Initiative, shorebird populations across North America have declined an estimated 70 percent since 1973. Of the 75 distinct shorebird populations breeding on the continent, about 30 percent have fewer than 25,000 individuals remaining. One particularly dramatic example is the rufa red knot, whose numbers have declined by 75 percent just since the 1980s.
Unraveling the exact causes of the declines is a little like solving a three-dimensional chess game where some of the pieces are missing. Shorebirds do not stay in one place for long, and they often cross borders, so international collaboration is needed to collect reliable data. Many species favor remote, hard-to-reach habitats—breeding in the Arctic, for example. And populations within the same species may follow different migratory routes, so birds spotted in a single flock may be coming from or heading to different locations. “These are hard birds to get precise information on,” confirms U.S. Fish and Wildlife Service (FWS) biologist Brad Andres, national coordinator of the U.S. Shorebird Conservation Partnership, a collective of state, federal and nongovernmental organizations working to develop and implement shorebird conservation strategies.
Biologists do know some of the myriad factors contributing to shorebird declines. In many locations, coastal and wetland habitats have been lost to development, and in habitats that remain, increases in beachfront recreation can disrupt nesting birds. Shorebirds that nest on inland prairies have lost habitat to agriculture. Meanwhile, populations of predators that readily coexist with humans, such as raccoons and house cats, have increased, taking a toll on chicks and eggs. And while hunting most shorebird species has long been outlawed in North America, it still occurs—both legally and illegally—on some birds’ wintering grounds in the Caribbean and South America.
Pollution is another threat, even in seemingly unspoiled locations. A study by researchers from McGill University and FWS found that the bodies of pectoral sandpipers, semipalmated sandpipers and red phalaropes nesting in apparently pristine Arctic habitat contained high levels of mercury. Found in emissions from coal plants and gold mining, this toxic metal travels far north in air currents, falling out into the wetlands where breeding birds forage.
A more recently recognized threat is climate change. Shorebirds require the right conditions in each of the many habitats they use, so they are among the wildlife species most vulnerable to changing climate. But until recently, conservation strategies to protect the birds tended to overlook this problem.
In 2014, biologist Hector Galbraith, then director of the Climate Change Initiative of the research nonprofit Manomet, and his colleagues published a landmark study in PLoS ONE modeling the impacts of climate change on shorebirds. Their conclusion: The criteria currently used to prioritize shorebird conservation efforts, developed in 2001, “underestimate risk because they do not explicitly include vulnerability to changing climate,” he says. As violent storms become more frequent, for example, long-distance flyers are likely to be harmed during their travels. Slowly rising seas, meanwhile, may be covering nesting beaches and stopover sites. “When we factored in climate change along with all the other threats to shorebirds, we found that 47 of the 49 species we evaluated were at a higher risk of extinction than scientists previously believed,” says Galbraith’s coauthor Michael Reed, a professor of conservation biology at Tufts University.
Climate change already seems to have dealt a double blow to rufa red knots. During spring migration, when they touch down for refueling on the shores of Delaware Bay, the birds are finding the tiny green eggs of horseshoe crabs, their major food, in short supply. That’s partly because the crabs have long been overharvested for bait and biomedical uses. But another culprit is 2012’s Hurricane Sandy, an extreme-weather event linked to climate change. The storm devastated large numbers of the beaches where the crabs come ashore to spawn. Without enough horseshoe crab eggs, red knots leave the bay without sufficient fat stores for the rest of their migration, so are less likely to survive the trip north.
For red knots that do make it to Arctic breeding grounds, warming trends can leave the larder bare there as well. In unusually warm springs, insects hatch early, so when the birds arrive to mate, lay eggs and rear their chicks, this critical food supply is past its peak.
Across North America, an expansive coalition is working hard to reduce threats to shorebirds. In addition to the U.S. Shorebird Conservation Partnership, PRISM (the Program for Regional and International Shorebird Monitoring) is a cooperative effort among U.S., Canadian and Latin American partners that focuses on population monitoring.
Beyond North America, international collaboration is also essential, and the rufa red knot is a case in point: As these birds move from their breeding grounds in the high Arctic to wintering grounds in Tierra del Fuego at the tip of South America, they cross as many as 40 U.S. states and 27 different nations.
“We knew almost immediately after the release of the first shorebird conservation plan in 2001 that it was irrelevant to plan just for the United States,” says David Mizrahi, vice president for research and monitoring at New Jersey Audubon, an NWF affiliate. “Most shorebirds move through entire hemispheres.”
In response to that realization, a coalition of North and South American government agencies, universities and nonprofits launched the Atlantic Flyway Shorebird Initiative that, in 2015, released a plan to protect 15 shorebird species that migrate between the continents. The goal is to boost the birds’ populations between 10 and 15 percent by 2025 using strategies that include protecting habitat as well as reducing predation, hunting and human disturbance. This April, the Pacific Flyway Shorebird Survey launched in the West. Meanwhile, New Jersey Audubon is working with partners in the United States, Brazil, French Guiana, Suriname and Canada to learn why semipalmated sandpiper numbers have dropped. (One survey documented an 80 percent decline in overwintering sandpipers in South America from the 1980s to 2011.) “I think these collaborative efforts are going to really move the needle on shorebird conservation,” Mizrahi says.
One such effort—this one among U.S. states to reverse American oystercatcher declines—began in 2008 with funding from the National Fish and Wildlife Foundation. Project participants stole a leaf from corporate playbooks, developing a “business plan” that lays out exactly what “return” is expected from each “investment” in conservation action. These actions include habitat protection (closing off nesting areas to vehicle traffic, for example), beach patrols, educational talks, signs telling visitors not to disturb bird nests and, on island nesting sites, trapping and removing predators such as raccoons and foxes. Their approach seems to be working: The North American oystercatcher population has increased by 10 percent since the program started.
A hint of that success materializes on Georgia’s Altamaha River when something stirs the oystercatcher flock on the sandbar to wakefulness. The birds raise their heads, stretch their wings and start calling, a loud, resonating wheep! “That’s territorial,” Keyes says. He points down the beach, where a pair of oystercatchers, separated from the flock, stand close together. “The birds that breed locally have already paired up,” Keyes explains. Will they have nesting success, helping to grow the oystercatcher population? The future is not clear ... but it’s a little brighter than it once was.
The National Wildlife Federation is working nationwide to protect and restore coastal habitats for shorebirds and other wildlife. On the Atlantic Coast, for example, the Federation is collaborating with several partners, including NWF affiliate New Jersey Audubon, to assess some 170 coastal impoundments from Maine to Virginia. Most of these manmade wetlands were designed to attract waterfowl to wildlife refuges. But they also make superb shorebird habitat. “We’re trying to understand the ecological and societal value of impoundments ... the number of shorebirds that use each impoundment and which impoundments draw the most bird watchers and other people,” says NWF Coastal Adaptation Specialist Taj Schottland. Adds New Jersey Audubon Senior Research Scientist Nellie Tsipoura: “We’re also looking at which impoundments are most vulnerable to flooding and erosion. We then provide refuge managers with recommendations to protect the habitats and reduce the likelihood of costly repairs.”
To learn more, visit coastalimpoundments.org.
Cynthia Berger wrote about the benefits of gardening for pollinators in the April–May 2016 issue.
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