KEY POINTS:
Four bar-tailed godwits have flown their way into the record books with nonstop flights of more than 10,000km from New Zealand to the Yellow Sea.
The godwits, tracked by satellite transmitters, did not stop to eat or drink on the first leg of their northern migration, which will end in Alaska.
Dr Phil Battley, an ecologist at Massey University's Palmerston North campus, said it had been suspected that the birds could fly such distances but now it had been proved.
No other animal had shown such endurance, he said.
Dr Battley said it was the first time transmitters had been implanted in New Zealand into the female birds, which took from 6 to 7 days to cover the route, flying up to 2km high at an average speed of 56 km/h.
Two of the birds had flown from Golden Bay at the top of the South Island and two from the Firth of Thames, covering distances of 10,063km to 10,205km.
Not all the monitored godwits, which started flying out in the middle of this month, had shown such stamina.
Dr Battley said that of the 10 godwits tracked so far, three had made stops - in Papua New Guinea, the Philippines and Micronesia. Interestingly, they were male birds, which had instead been fitted with backpack tracking devices, worn on the outside and fitted with a harness.
While those transmitters, at 9.5g, were lighter than the implanted devices, weighing 22g, they appeared to create drag problems which could explain the need to stop on the way, he said.
Dr Battley said godwits flew in reasonably small flocks of 30 to 70 birds, and if one touched down it was probable that the flock had landed.
When the godwits set out from New Zealand they are clinically obese, but they lose about half their bodyweight in each leg of the migration.
Upon arriving in the tidal flats of the Yellow Sea, off China and South Korea, they would land with drooping wings, have a big drink and then stay on for a month or two to refuel.
"It's the equivalent of riding the Tour de France but keeping it up for a week nonstop."
The godwits would then head to Alaska where they were expected by mid-May.
In September they would return, flying in a straight line across the Pacific Ocean to the New Zealand coast, from Parengarenga Harbour in the Far North to Invercargill.
Dr Battley said the surveillance project had been funded by the United States, which was interested in the birds' movements because they were potential carriers of the H5N1 bird-flu virus to Alaska.
But he said that was not a threat to New Zealand, as by the time they returned here it was some months since they had been in Asia and shorebirds had not yet been found to have H5N1.
The project would also provide crucial information about the migratory behaviour of declining species, he said. Throughout East Asia and Australasia, 85 per cent of shorebird populations were declining, and 40 per cent of shorebirds inhabiting Oceania were classified as threatened or near threatened.
Dr Battley said annual population counts at major sites in New Zealand showed a decline in numbers.
The increasing reclamation of tidal mudflats in Korea and China and the change in geography caused by dams such as the Three Gorges Dam were also affecting birdlife.
"We are entering a critical decade for these birds, so the research is timely and crucial."
