An unlucky godwit halfway through his migration from Alaska to New Zealand has turned back after hitting strong winds over the Pacific Ocean.
The male godwit, known as 4BRWB because of the bands on his legs, left the tidal flats in Alaska's Yukon-Kuskokwim delta on 11 September before encountering the strong winds 2000 kilometres into his journey.
Massey University associate professor of Zoology Phil Battley said 4BRWB finished up back at his Alaskan take-off point after 57 hours of constant flight, which seemed like a lot to a human, "but it's not that much to a godwit".
Battley is an ornithologist and godwit expert with a long association with the Pūkorokoro Miranda Shorebird Centre.
He said the turnaround mid-migration, after 33 hours of flying, was unusual. It was the first time a tracked godwit had turned around because of strong winds.
4BRWB was one of 20 birds fitted with radio transmitters in November 2019.
"He's still got time. He won't have used all his energy - he's just realised he was facing headwinds and thought 'this isn't a good start to a 10-day flight' ... and turned back."
4BRWB weighed 284 grams when he was banded. He is estimated to have weighed 500 grams when he took off from the Yukon, burning his fat reserves over the 11,000km migration.
Other godwits who left Alaska at the same time have made it to our shores, with godwit-watchers reporting an influx of the birds over the last week. But it's also possible others opted to turn back.
4BRWB was tracked on his migration to New Zealand last year where he also had to contend with strong winds.
"Last year, he also had difficult winds - strong easterlies - and he stopped in New Caledonia for a month, before eventually coming back here. If it's been hit by a problem two years in a row, I think you can call it unlucky!
"But he's a bird who knows how to survive by adjusting his behaviour when he has to. Another amazing thing about this bird is he left Yukon on exactly the same date this year as he did last year."
Battley said 4BRWB would not have used up all his energy and there was interest in how long he rested for and the route he took back to New Zealand.
The godwits' 11,000km non-stop migration is one of the longest in the avian world. Last year, a male godwit - 4BBRW - created international headlines when it set what many believe to be a new distance record for the species for the Alaska-Firth of Thames flight, covering more than 12,000km in 9.5 days.
Department of Conservation technical advisor Bruce McKinlay said the research tools being used in this study were allowing those monitoring the species to assess the impact of weather on ultra-long-distance migration in real time, and also understand how adaptable to changing weather migrating godwits were.
The research is helping to build networks of protected areas in East Asia and supporting Department of Conservation's work in China and South Korea.
The real-time reporting of birds stopping over in South Korea in the Northern Hemisphere spring this year was used to enhance boundaries of World Heritage site nominations.