Friday, August 29, 2008

What’s In A Name? The Godwit or Kuaka

The bar-tailed Godwit or Kuaka

The bar-tailed godwit or kuaka, its Maori name, is a migratory bird that spends the southern summers in New Zealand then migrates northwards to Alaska, via China, Japan, and South Korea, for the breeding season, returning in the southern spring. Its trans-Pacific migration includes one of the longest known non-stop migratory paths.

In preparation for its migration the godwit puts on 60%–70% of its weight. By departure 55% of its weight is fat since fat is both light and yields eight times more energy than muscle protein. While seasonal changes in day-length trigger hormonal changes to initiate migratory preparations, the godwit’s navigation over such long trans-Pacific flights is thought to be guided by a combination of cues, including the earth’s magnetic map, sun angles, star movements, flock behaviour and memory, and landmarks to correct its course as it travels.

In 2007, the inimitable “E7”, her tag reference for satellite tracking, posted a trans-Pacific journey of 18,000-mile-long (29,000 km) series of flights tracked by satellite, including the longest non-stop flight recorded for a land bird.

E7’s Remarkable Trans-Pacific Journey

Source: US Geological Survey Alaska Science Center

On 17 March 2007, E7 departed Miranda in the North Island of New Zealand, flying non-stop to Yalu Jiang, China, completing the 6,300-mile-long flight in about eight days. After a 5 week stopover, she departed on 1 May for the Yukon-Kuskokwim River Delta in western Alaska. On this five day 4,500 mile non-stop leg of her journey, she crossed the Sea of Japan, Northern Pacific, and the end of the Alaska peninsula.

The breeding grounds in Alaska are tundra, moss and swamps, rich in insects that the godwits feed on. Godwits almost always lay 4 eggs and the chicks can fly after about 29 days, with the parents leaving the chicks soon thereafter. After breeding, the godwits move to the shorelines and estuaries along the Alaskan coast to fatten up on shellfish and sea worms for the return flight to New Zealand.

The most remarkable flight of E7 was her return journey to New Zealand – some 7,200 miles non-stop in eight days from Alaska to New Zealand. It is longest non-stop flight recorded for a land bird.

Since kuaka are land birds, they are unable to stop to eat or drink while flying over open-ocean. The constant flight speeds at which E7 was tracked by satellite indicate she did not stop on land.

On her arrival back in New Zealand, E7 touched down at a spot just 8 miles east of where she had been tagged before she started her pan-Pacific journey.

It’s estimated that over the course of a 20 year lifetime, a godwit’s migratory mileage could top 288,000 miles.

In addition to locations in the North Island such as Manukau and Kaipara Harbours, and the Firth of Thames, the kuaka roost in large colonies at Farewell Spit and the Avon-Heathcote Estuary in Christchurch in the South Island.

Every southern spring, a watch is kept for the harbingers of spring on the Avon-Heathcote Estuary. Upon the first arrival, the bells of the Christchurch Cathedral are rung for 30 minutes to herald their arrival.

Upon arrival, the kuaka appear bedraggled having exhausted their fat reserves during the long journey. Their roosting colony at the Estuary is on the South Shore Spit in South Brighton. The kuaka fan out to feed at lowtide, foraging over the mudflats and shoreline for molluscs, crabs, marine worms and aquatic insects, probing the mud with their long bills as the tide recedes.

The Avon-Heathcote Estuary – the godwit colony is at the southern tip of South Shore Spit

In February-March, the godwits are farewelled by residents of Christchurch as they leave on their northern journey.

Kiwis of the human kind in the far flung Kiwi diaspora around the globe might adopt the godwit or kuaka as their emblem. However far they may be from their multiple homes, they can look to this humble bird for inspiration on how to close the distance between them.

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