Alaska shorebird suffering from troubled Asia winter grounds

Alaska shorebird suffering from troubled Asia winter grounds

The population of a plump northern Alaska shorebird weighing just over 2 ounces has been declining for decades. Reversing that decline will require additional conservation efforts at some of the birds' East Asia wintering grounds, according to new research.

Development that has replaced coastal wetlands is considered a major factor in the decline of the arcticola dunlin, an Alaska-breeding subspecies.

Benjamin Lagasse, a doctoral student at the University of Alaska Fairbanks, has been studying the arcticola dunlin since 2016. His latest research was published earlier this year in Diversity and Distributions.

Co-authors include professor Greg Breed in the UAF Department of Biology and Wildlife and researchers from the U.S. Fish and Wildlife Service, Wildlife Conservation Society and Manomet Conservation Sciences.

"To our surprise, we found populations that wintered along the East China Sea and Japan were the sources of the decline," Lagasse said. "Additional conservation efforts in these regions are likely needed."

"What those conservation efforts should be is unclear, but we are now able to focus our attention at the source, pinpoint losses and reverse the decline," he said.

Population trends in arcticola dunlin can reveal the health of both their Arctic breeding grounds and the wetlands they rely on during migration between Alaska and Asia.

By tracking demographic rates such as births and deaths, scientists can better identify where declines are occurring and whether problems stem from conditions on the breeding grounds, along migration routes or at wintering areas.

Arcticola dunlin breed in northern Alaska and winter along the Yellow Sea, East China Sea and Japan. A second dunlin subspecies also breeds in Alaska but winters along the Pacific Coast of North America and is not considered at risk.

The arcticola dunlin population has been declining by up to 16% annually.

"That is an exceptionally rapid rate of decline," Lagasse said.

Some of the steepest declines in Alaska have appeared on the coastal plain of the Arctic National Wildlife Refuge.

Lagasse combined nesting records and tracking data collected in northern Alaska to estimate survival rates and population trends for birds wintering in different parts of Asia. Researchers located nests near Utqiaġvik and along the Ikpikpuk and Canning rivers and marked nearly 200 adults for tracking.

Habitat loss is a key factor in population decline. It forces shorebird species onto remaining wetlands that may or may not have enough food and space to support larger numbers.

"Differences between regional dunlin populations in the intensity of their declines were most likely linked to conditions on their wintering grounds," Lagasse said.

Previous studies found major declines in dunlin populations in Japan between 1975 and 2008. About two-thirds of tidal flats have been converted for development since the early 1960s, but that has slowed.

"Dunlin in Japan appeared to be undergoing a rapid decline despite relatively little ongoing habitat loss," Lagasse said, "perhaps because birds that were displaced or otherwise struggling lacked sites that they could turn to that could support larger numbers of birds."

The East China Sea population is declining rapidly, possibly because birds become entangled and die in razor clam nets, though Lagasse said more research is needed to understand the exact causes of the population declines.

Lagasse found the Yellow Sea population to be "surprisingly stable" despite significant continuing habitat loss.

"I suspect this reflects that dunlin in the Yellow Sea tended to have alternative sites that they could turn to that, fortunately, could support larger numbers of birds."

It's not only the reclaiming of tidal flats for development that matters but also how humans use that reclaimed land. Previous research found major regional differences.

In the East China Sea and Japan, nearly two-thirds of reclaimed sites were agricultural areas and only 2% were salt production ponds. Along the Yellow Sea coast, nearly half of reclaimed sites were salt ponds and 13% were agricultural areas.

The Yellow Sea salt ponds provided the alternative habitat that Lagasse noted. They were about 15 times larger than agricultural sites in the East China Sea and Japan and supported 45 times more shorebirds because they provided higher-quality feeding habitat, according to the research paper.

Lagasse said more research is needed to better understand the exact causes of the population declines.

"Alaska's shorebirds migrate vast distances, and conserving them often requires an international approach," he said.

ADDITIONAL CONTACTS: Benjamin Lagasse, [email protected]; Greg Breed, [email protected]

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