The top-secret layovers of our migratory birds

New Zealand’s migratory birds, many about the size of a blackbird, make an epic journey thousands of kilometres across the globe each year.

The layover locations where they rest and re-fuel in the middle of their migration have sometimes been shrouded in mystery.

GPS data and forays into off-limits areas are changing our knowledge of their journeys. Some birds lay over in Japan, others in Guam. Some choose the unlikely stop-off of North Korea.

In some cases, this information is shedding light on why we have fewer arrivals from some species.

The number of New Zealand’s Pacific golden plover, or kuriri, arriving in New Zealand has declined from thousands to 200 to 300 in recent years. The birds, officially natives as they spend more than half their life on our shores, have been coming to New Zealand for thousands of years.

The Pūkorokoro Miranda Shorebird Centre has a project tracking the plovers’ journey. Three birds were tagged as a result of months of efforts by volunteers, and with the help of international plover experts. Project coordinator Jim Eagles has been following the GPS signals with huge excitement.

“Until now we’ve known very little about them. We don’t know where they breed, what route they take to get here, where they stop over on the way or, most importantly, why their numbers are declining.”

It was suspected the birds might be experiencing issues somewhere along their migratory path.

The three tagged plovers, nick-named JoJo, Jim and Amanda after project team members have all sent back data from their journey.

Amanda and JoJo stopped in Japan after a 9000km non-stop flight. It’s suspected they may be on their way to Alaska. Jim, whose physique suggested he may be most likely to be heading to Siberia, has stopped in Guam.

Eagles said experience has shown problems that may lead to fewer birds arriving often stem from problems along the birds' migratory path.

In Japan, the GPS data for one bird shows an area with rice paddies and a coastal estuary.

The migratory paths so far of JoJo, Amanda and Jim. Image: Supplied

Adrian Riegen of the New Zealand Wader Studies Group was the lead bander on the plover project. He explained sometimes the issue stemmed from a lack of food caused by urban sprawl eating up habitat.

In South Korea, he’s seen the shift to using chemicals in farming affect birds’ layover food sources.

“Even in the rice paddies where potentially they get can get food, now the farmers do a lot of pest control for insects. They don't like a lot of grubs and beetles and things in their rice paddies.”

While New Zealand can’t force Japanese or South Korean farmers not to spray insecticides, having an idea what the issue is could be helpful.

“That's the big thing with science. If you want to protect something but you don't know anything about it, it's very hard to protect it. Once you know, then maybe you can do something.”

The current theory is the habitat and pressures on their food sources are changing so much, the birds can’t complete their annual life-cycle.

“If you can’t get food at one of the places when you fly 9000 km, then you either hang around there until you die, or you battle on towards the Arctic and maybe you run out of fuel on the way and fall out of the sky and die.”

Riegen is currently in North Korea surveying shorebirds. It’s his seventh trip there and the repeated visits are thanks to Winston Peters.

In 2007, Peters visited North Korea as part of denuclearisation talks.

“We saw this as an opportunity to ask if we could go there,” said Riegen.

Peters posed the question and two years later Riegen and others made their first trip and commenced on a project surveying the Yellow Sea coast of North Korea. Without Peters' support, he suspects requests would have got nowhere.

The project aims to identify the areas migratory birds are using, as well as the species and numbers visiting.

Under the watchful eye of Korean scientists (who act as minders), this year he’ll venture into areas no foreigner has been to since before the Korean War ended in 1953.

He said millions of birds stop in North Korea, including bar-tailed godwits and red knots from New Zealand. Understanding the areas which are important is crucial to help in any conservation.

“One of the problems is that these mud flats are really used for a couple of months in the spring and a couple of months in the autumn each year by these birds and during the winter and the summer and there's not too many birds there.”

Riegen said that made it easy for locals to think the flats weren't used at all.

“But for the two months, each season that they are there, those mudflats are absolutely vital to them. Without them they can't get the fuel they need for the journey. The link is broken and the birds end up dying.”

The poverty in the area could work in the birds’ favour, according to Riegen. Because the birds eat insects which affect crops, they can save the farmers food - and money, by reducing the need for insecticides.

During this trip, Riegen said the team is also visiting two secondary schools in Pyongyang to talk to students about birds and conservation.

He hopes some of what the children learn will be remembered as they move into their careers, and perhaps one day they’ll be in a position to make decisions to help preserve migratory birds’ layover habitat and food.

For the mysterious Pacific golden plovers, it’s hoped the three birds carrying GPS tags make it to their breeding grounds, and the tags continue to transmit their journey home to New Zealand.

Read more: Tracking the mysterious kuriri

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