Going the extra mile: migratory birds in New Zealand

It is not only people that enjoy going away for a winter holiday in the sun; as the seasons change, New Zealand’s international migratory bird species also fly the coop in the pursuit of warmth, daylight and a plentiful food supply.

In springtime, thousands of birds that breed in the Arctic migrate to New Zealand to escape the perilous northern hemisphere winter. They flock to intertidal mudflats throughout New Zealand, the most important of which are the Firth of Thames and Manukau Harbour. These birds spend spring and summer foraging, moulting and fattening up before migrating back to their northern breeding grounds in autumn.

It is estimated that approximately 90,000 bar-tailed godwits, 35,000 lesser knots and 5,000 ruddy turnstones make this journey to and from New Zealand each year. Another half-dozen species are also regular visitors (50-700 birds), such as Pacific golden plovers and whimbrels.

The 11,000-12,000 km journey that godwits undertake while migrating southwards to New Zealand is the record for the longest non-stop flight conducted by any bird species in the world. This remarkable flight takes 8-9 days, flying at an average speed of 56 km/hour.

In preparation for this long-haul flight, godwits put on extra weight, develop larger flight muscles and shrink their stomach, liver and kidneys as these organs are not required on the journey. On arrival, the godwits are exhausted, half their original weight, and are ready for their first meal in days!

Other migratory bird species break up the journey to New Zealand by making coastal stopovers along the Yellow Sea region to rest and feed. Godwits also stop at these staging sites to rest and refuel on their northward migration.

The extensive and increasing loss of these vital intertidal mudflat staging sites as a result of reclamation for development purposes is a real concern. Given that this loss is occurring overseas, conservation measures in New Zealand are largely limited to protecting migratory bird habitats here in Aotearoa, as well as advocacy and research.

To help get a better understanding of where the birds go and which sites are of most importance, regular bird banding and monitoring programmes are conducted, particularly in the Firth of Thames at Miranda and at Foxton Estuary. By attaching small white flags with a band to the upper legs of some of these migratory birds, people in New Zealand and overseas can identify and report these birds which, together with other research, helps paint a better picture of their migration pathways. The information gathered is being used to help preserve these vital stopover habitats and aid the survival of these remarkable species.

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For further information please contact Karin Sievwright or Dr. Lee Shapiro