The Turnstone on turnstones
Honouring a little bird with a big story
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I’m not fond of winter, so as we get closer to the shortest day of the year, I am already thinking about the heralds of spring. I’m watching the grey-green leaves of my daffodils as they push their way above ground, and anticipating the cheerful yellow of their flowers. I’m looking forward to the taste of fresh asparagus. And I’m thinking about the distinctive call of the shining cuckoo, a whistling note that rises upwards in pitch, repeated half a dozen or more times, then one single falling note.
The call of the shining cockoo is never heard in the winter, at least not in New Zealand, because the birds aren’t here. When autumn comes, they fly north, heading for the Solomon Islands and Bismark Archipelago, to the east of Papua New Guinea. They return again in the spring, usually late September or October in Wellington, their calls telling us that winter has well and truly departed.
When, in 1845, the Reverend William Colenso claimed that the shining cuckoo was migratory, a fact told to him by Māori, the claim was greeted with incredulity by other European naturalists. At that time, the greatest distance that Europeans knew of birds migrating was from one end of Europe to the other. New Zealand was thought to be too far away from anywhere to have migratory birds.
In fact, the journey of the shining cuckoo isn’t particularly remarkable. It travels 2-3 thousand kilometres, only a moderate distance in comparison to the journeys of some wading birds. The best known of these is the bar-tailed godwit, or kuaka, a long-legged wading bird that flies from Alaska to New Zealand every spring and then back again in the autumn. But there are others, among them a stout brown bird with a white chest, around the size of a blackbird. It’s known as a turnstone, or more specifically a ruddy turnstone, for its habit of searching for food by looking underneath stones. It’s not a conspicuous or spectactular bird, but it’s an icon of curiosity and determination as it pokes around on the seashore in its search for food.
A few thousand turnstones turn up in New Zealand every spring, only a fraction of their global population, which is estimated to be in the hundreds of thousands. However, exact numbers are difficult to calculate for migratory birds, especially for something like a turnstone, which can be found in dozens of different countries. It breeds in the Arctic, in sparsely populated parts of Alaska, Canada, Greenland, Russia and Scandinavia. In the Arctic winter, it heads south, sometimes as far as the sub-Antarctic Campbell Island and Patagonia.
It’s even more difficult to know what is happening to populations of migratory birds – whether they are stable, increasing or decreasing. Overall, the turnstone is thought to be declining, but exactly how much is uncertain. In some places, such as Finland and Japan, the decline has been marked and well-documented. There has been a decline reported in Namibia too, perhaps connected to the decline in Finland, since the birds that breed in the north of Europe travel south to Africa. In other places, such as Canada, it’s thought that turnstones have decreased significantly, but nobody is quite sure by how much. With a bird that breeds in such remote and sparsely populated areas, it’s simply difficult to know.
The decline of turnstones in Finland has been attributed to local conditions, such as increased predation by American mink and increasing vegetation cover in breeding areas. But the decline of turnstones is part of a more general trend among Arctic wading birds. Half of Arctic waders are declining, and the figure is much higher for those that travel down through east Asia and on to Australia and New Zealand. What’s going on with these birds?
One of the biggest threats to migratory birds using that route (known as the East Asian-Australasian Flyway) is the condition of an area of sea that sits between China and the Korean Peninsula. The waters of this sea, known as Huang Hai in Chinese, Hwanghae in Korean and the Yellow Sea in English, are coloured by the sediment that flows down several major rivers, including the Huang He (Yellow) River. The Yellow Sea is, or was, fringed by more than a million hectares of tidal flats that are critically important for birds that pass through the area. Now, around 40% of the tidal flats have been reclaimed, and the waters are heavily contaminated and over-fished. The migratory birds that depend on this area are among the most threatened.
The turnstone is not among the species considered to be endangered, at least not yet. It is still common and its population is widely dispersed, which protects it from localised loss of habitat and pollution. But there’s another threat to migratory wading birds like the turnstone, and it’s not a threat that’s confined to a few areas. The Arctic is warming at twice the global average rate, which means that the species living there are dealing with a wide range of environmental changes. Trees and shrubs are growing further north, encroaching on the tundra habitat where turnstones nest. The seasons, and therefore the times when food is available, are changing. The melting of permafrost is changing the way water moves through the Arctic landscape, changing the plants communities and therefore the habitat for all the species that live there.
Exactly what this means for the turnstone is uncertain. So far, populations of Arctic migratory birds are mostly affected by what’s going on outside the Arctic. Some species, notably geese, are doing well and actually increasing. But for the turnstone, already in decline, further changes to its environment are unlikely to bring good news. As the world heats up, we are likely to have our minds on other things – our own health and economic viability, and the need to accommodate a growing number of migrants fleeing ever-worsening conditions in their home countries. But the turnstone and other migratory birds are worth remembering, They are a pointed reminder of the connected nature of our global environment.
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