Watching the elegant oystercatchers probing an expanse of mudflats at Cornelian Bay I found it hard to imagine that anyone would want to do them harm.
I always head to the shores of the Derwent when I need a pied oystercatcher “fix” but my latest shorebird excursion to Cornelian Bay coincided with a disturbing report from New Zealand. A closely related species, the South Island oystercatcher, had raised the ire of commercial clam collectors there who called for its cull.
In response, a team of researchers set to work to establish whether the oystercatchers were in fact responsible for a rapid decline in clams at Ripiro Beach, north of Auckland.
Monitoring the birds’ feeding habits, the team from the University of Waikato in Hamilton discovered the oystercatchers did not take large numbers of the toheroa clams, a traditional Māori delicacy, which usually bury themselves too deep in sands for oystercatcher beaks to reach.
The oystercatchers preferred a smaller clam species and other shellfish which were not commercially harvested.
The researchers found in their study a reason for the clam decline could be a lack of fresh water washing over the clam beds, which was essential for their good health. Water reaching the ocean had been disrupted in recent years by the establishment of thirsty pine plantations along water courses further inland.
The saga exposes our lack of knowledge about not just oystercatchers but wading birds as a whole, a neglected and overlooked area in the great world of birds.
The myriad waders in all their forms and guises are usually out of sight and out of mind because they tend to inhabit inaccessible places. The oystercatchers, though, find a happy home on the fringes of suburbia and are easy to find along shores and even, on occasion, on grass verges where they spear worms with their long, knitting needle beaks.
The New Zealand research, reported by the Australian ornithological science journal Emu earlier this year, proves a salient point. Because we know so little about shorebirds we should be wary of jumping to conclusions about their impact on the human world.
Shorebirds across the planet are in sharp decline. Many migrate vast distances and so are vulnerable on these trans-continental journeys, but the threat can extend to the sedentary ones, like the oystercatchers and to a lesser extent, another of the wader clan, the masked lapwing, or plover, so common in Hobart.
In Australia, the danger comes from the loss of coastal habitat because of building and agricultural development, and disturbance on beaches where most of the shorebirds that breed in Australia nest.
Although the pied oystercatcher remains secure in Tasmania –which holds about 30 per cent of the global population – it has vanished from vast swathes of the country’s south-east. In New South Wales, for instance, it is classed as an endangered species.