Bar-tailed godwits (Limosa lapponica) are the most common Arctic migrant to New Zealand. In 2005 scientists reported that they make the longest non-stop flight of all birds – an amazing 11,000 kilometres from Alaska to New Zealand, in only eight or nine days. It was already known that the departure and arrival were only days apart. The hunch that godwits fly over open ocean and outside any coastal migration route had also been supported by traditional Polynesian accounts of the birds, known as kūaka, flying over the Pacific Islands on their way south. In addition, godwits banded by researchers in Alaska had not subsequently been sighted along the East Asian–Australasian Flyway during their southward migration.
The southern migration
When it is time for the godwits to migrate south, they wait for storms that provide them with tail winds of 40–80 kilometres per hour for the first 1,600 kilometres. Observers report that when the birds finally reach New Zealand they fall asleep, but within hours begin feeding to replenish what they lost en route – about half their body weight. Three months later, in preparation for the northward return flight, they start to stock up on food, doubling their body mass.
Arriving from late September, during the southern hemisphere spring, the majority of the 80,000–100,000 godwits head for Kaipara and Manukau harbours, the Firth of Thames, Farewell Spit, and the Avon–Heathcote estuary near Christchurch. In large flocks they feed on molluscs, crabs, marine worms and aquatic insects, probing the mud with their long bills as the tide recedes.
These relatively large waders average 40 centimetres and 325 grams, the females heavier than males. Brown with a long bill and medium length legs, they turn ruddy red when they are plump and ready for the return journey.