It is a Sunday morning at Ohiwa Spit and we are there for the winter wader count for the Ornithological Society. It is one of those lovely, fine, calm winter days when, as one of my companions says, one has to thank the universe, God or whatever, for just being alive.
It is approaching high tide and the birds are still flying in to roost on the Spit. As the tide encroaches on their feeding grounds, the birds look for a place to roost until the tide moves out again. It is these habitual roosting sites which give us the opportunity to count the birds with some accuracy and reliability.
In view of the increased impacts of human influences on wader habitats the Ornithological Society of New Zealand initiated the National Wader Count scheme in 1983. The aims of the study are to determine firstly the numbers and distribution of waders occurring at coastal sites throughout New Zealand, secondly, the seasonal changes in the distribution and numbers of waders and thirdly, the annual changes in the numbers of waders.
In the Bay of Plenty, members of the Society count waders at Tauranga Harbour, Little Waihi and Pukehima Spit, Kaituna Cut and Maketu Estuary and Ohope Spit and Ohiwa Harbour.
We count 18 Tuturiwhatu, the New Zealand dotterel, many of which are already in their breeding plumage. They just move away as we approach and do not fly off. These birds are so vulnerable, their very name meaning that they are easy to catch.
Poaka, the pied stilt, Tara, the white-fronted tern are on the spit in numbers. Torea, the South Island pied oyster catcher, SIPOs as we affectionately call them, are also there in numbers but scattered about. The stilts and the SIPOs nest along South Island braided rivers and lakes and migrate to the north of New Zealand to avoid the southern winter.
There are a couple of Taranui, caspian terns and 700–800 Kuaka, or godwit. The godwit’s extraordinary long upturned bill characterises an otherwise rather plain unassuming bird, considering its legendary reputation.
Between 85,000 to over 100,000 Bar–tailed Godwit visit New Zealand annually. However, from 8,000 to 18,000 birds, roughly ten percent, remain to winter over in New Zealand, presumably mainly juveniles as few are in breeding plumage. It is these birds that we are counting.
Two subspecies of Godwit are currently recognised but, according to the Heather and Robertson Field Guide, this is under review. Limosa lapponica breeds from Scandinavia east to central Siberia and migrates to Europe, Africa and southern Asia. Limosa Baueri breeds from the Lena River across eastern Siberia into northern Alaska and migrates to southeastern Asia, Australia and New Zealand.
Adult bar–tailed godwit probably migrate the 11,000 kilometres to New Zealand from their breeding grounds in western Alaska directly over the Pacific although perhaps some travel via one or two staging areas in north eastern Asia and northern or eastern Australia. The journey from Alaska to New Zealand is an astonishing flight, the longest non–stop bird migration in the world.
Beringia is where the godwit begin their journey. This tendril of land where Asia and America nearly touch is a global cross roads, a springboard for millions of migratory birds of a variety of species. Mingling with the bar–tailed godwits bound for New Zealand, are Hudsonian godwits, aiming for Tierra del Fuego; northern wheatears traveling across Asia for wintering grounds in Africa, and Swainson’s thrushes moving south to the equatorial forests of Venezuela and Brazil.
Godwit along with other migrants start arriving here about mid–September and disperse throughout the country including the Chatham Islands. They flock in a few favoured places, including the Firth of Thames. When these migrants arrive they are lean, tired, hungry and bedraggled, just feathers and bones, and the long legs and bills look even longer.
They leave New Zealand in March and early April and arrive in Alaska in May and early June. The return route is probably via northern Australia or New Guinea, and northern Asia rather than directly across the Pacific.
American scientists have recently unlocked the secret of the extraordinary migration of the New Zealand sub species of the bar–tailed godwit. As reported in the New Scientist, the birds go on a binge, a feeding frenzy, before their long haul flights until up to 55 per cent of their weight is fat. They then reduce the size of their gut, kidney and liver by up to 25 per cent to compensate for the added weight. Obese with fuel, freed from the baggage of a heavy guts, the godwit are ready for the air. The scientists think that the birds reshuffle proteins in their bodies before they set out and that this allows them to reduce the size of their food-processing organs.
