One of my favourite harbingers of spring on the Hibiscus Coast is the arrival of our bar-tailed godwits, or kuaka.
Flocks of these magnificent shorebirds can be easily seen on tidal mudflats all along our shores, for example in the Ōrewa Estuary and Long Bay/Okura Marine Reserve. They use their long bills to probe deep into the mud to catch invertebrates.
They return here from their breeding grounds in Alaska, and perform the most dramatic migratory feat currently known of birds.
After they finish nesting, and before the harsh Arctic winter sets in, they rapidly store up fat reserves and depart for their wintering grounds here in NZ. Their flight is remarkable: they make a beeline across the Pacific and fly 11,000km for nine days straight. When they finally make landfall, they arrive on our coast 40 percent lighter, hungry and exhausted.
Ornithologist Phil Battley, an Associate Professor at Massey University, has been studying bar-tailed godwits for years. With the recent development of miniaturised tracking technology, Dr Battley and his colleagues have resolved the details of their flight paths in exquisite detail. And their research has shown that things often do not go as planned for the poor kuaka.
Consider the tale of 4BWRB – an absolute legend among godwits. He was caught in 2019 at the Miranda Shorebird Centre and fitted with a small solar-powered satellite tracker that provides data on his position every few hours. The device weighs less than 2 percent of the bird’s weight and is still going strong today.
On September 10, 4BWRB set off on his journey back home. Normally they try to leave with a strong tailwind that gives them a good head start but this year 4BWRB miscalculated and hit strong head winds. After 33 hours flying, he turned around and headed back to Alaska, making a 4000km, 57-hour flight for nothing.
His departure window from Alaska was shrinking because winter conditions set in quickly. He had used up valuable fat reserves on the first attempt and had to refuel before trying again. After 11 days of hearty eating, he departed again – this time with strong favourable winds. He was off!
Godwits can usually time their departures with good conditions – but it is much harder to predict what they face on arrival. As he approached NZ, he again ran into unfavourable winds – a strong southeasterly pushing him back. Seven days and 10,000km in, the last leg of the journey seemed too precarious. What was he going to do?
But there is a safety net for godwits as they approach NZ – many Pacific Islands can offer refuge. On September 30, 4BWRB decided to quit his trip again – and veered east on a new bearing. He then made landfall in New Caledonia, which is where he is as I write this. He will chill there for a few weeks, and when he is good and ready, he’ll set off on the final leg of his journey home to Aotearoa.