Wading birds are a varied group belonging to the order Charadriiformes, which also includes gulls and terns. Some waders are found only in New Zealand, and may not even travel far from their birthplace. Others breed in the northern hemisphere and migrate thousands of kilometres to New Zealand shores. Wading birds found in New Zealand belong to these groups: oystercatchers; stilts; plovers and dotterels; snipes, sandpipers, godwits and curlews; phalaropes. Including rare strays and vagrants, 60 species have been recorded.
Adaptations of waders
What waders have in common is water: most feed in or near shallow water at estuaries, harbours, mudflats and beaches, or inland at lakes and rivers. Each species has adapted to a particular zone between the high and low tide lines. The length of their legs is a clue to whether they only feed at the edge or can venture some way into the water. Apart from some phalaropes, their toes are not webbed and they rarely swim.
The shape of waders’ bills also varies according to how they feed. If they peck near the surface (like dotterels), it is short. If they feed in water (like stilts) or probe deeply in mud (like godwits), it is long. Wrybill plovers have a sideways bend to the bill for gleaning insects and larvae from under stones.
Typical foods of wading birds at coastal sites are marine insects, small crustaceans, marine worms and shellfish buried in mud and sand in the rich intertidal zone.
Although most live on the coast for part of the year, many waders move inland to river and lake edges, pasture or open high country to breed. Their diet changes to include aquatic insects and larvae, fish eggs and worms.
Some of the rarer species, such as the black stilt, the Chatham Island oystercatcher, the shore plover and the New Zealand dotterel, are endemic to New Zealand – they are found nowhere else. Breeding along the coast or riverbeds, many wading birds are at the mercy of predators that eat their eggs and chicks. Vehicles may disturb or destroy the inconspicuous nests.
All New Zealand’s wading birds, except the spur-winged plover, are currently protected by law.
Māori were keen observers of wading birds. In Northland, godwits gathering for their annual migration to the northern hemisphere reminded them of the souls of the dead preparing to journey to the underworld. A Hokianga poet lamented:
Rarangi noa ra te rangai kūaka,
Kia tauhikohiko he pari tu waho.
Flocks of godwits are gathering,
Moving restlessly on the seaward cliffs. 1
In a prophetic song, a writer imagines a time when enemies will devastate the land, eliminating all people and leaving only the oystercatchers and dotterels:
Ko wai rawa te tangata hei noho mo to whenua?
Ko Turiwhatu, ko Torea, ko ngā manu matawhanga o te uru!
Who will be the people to live in your land?
Dotterel and Oystercatcher, the birds of the western shore! 2
While some waders don’t migrate, or migrate only within New Zealand, others (such as sandpipers, godwits and curlews) travel astounding distances from northern hemisphere breeding grounds to New Zealand. The related New Zealand snipe does not share their flying ability, and remains on outlying islands all year. Waders typically fly with strong, regular wing beats and a rapid flight.
Light as a sparrow at just 30 grams, the red-necked stint flies the remarkable distance of 10,000 kilometres, in stages, from the Arctic to New Zealand every year. It is the lightest wader to make this migration regularly.
Except for banded dotterels, some of which cross the Tasman Sea to Australia after breeding, the waders that breed in New Zealand stay within the country year round, some moving between southern and northern regions. New Zealand has a diverse range of habitats and a temperate climate, so there is no pressure to migrate away.
Many of the migratory waders from the northern hemisphere follow routes described as flyways. One of the most popular is the East Asian-Australasian Flyway, which allows birds to stop off and refuel in Japan, the Philippines, Papua New Guinea and Australia. Remarkably, one species, the bar-tailed godwit, makes the 11,000-kilometre trip from Alaska non-stop across the open ocean.