Toheroa beds under threat
Recovering toheroa shellfish beds near Dargaville have suddenly gone into decline.
Some Northland beachgoers are calling for a cull of protected shorebirds they say are responsible.
But a shorebird expert says this is a case of "ecology in action" with other factors almost certainly involved.
Found mostly on the northern west coast, toheroa shellfish numbers plummeted from over harvesting 40 years ago and the fishery has been closed ever since except for customary gathering under the permitting system.
The beds were slowly recovering well in the area, but have been hit hard over the summer by South Island pied oystercatchers, Dargaville stalwart Des Subritzby says.
A large group of the birds have taken up residence in the north Kaipara Harbour village of Kelly's Bay, and some coasters are blaming them for the big drop in numbers of the protected native shellfish from Ripiro Beach over the peninsula on the west coast.
The coasters have concerns the birds may eat out shellfish at beaches further north unless they are stopped, and they have even approached Northland MP Mike Sabin to intervene.
While Christchurch-based shore bird expert John Dowding says the birds might be able to reach younger shellfish, he doubts the birds could get their beaks down deep enough to eat deeply buried adults. Dowding suspects there are broader issues involved with the toheroa decline.
The harbourside community estimates bird numbers at around 4000 and say they have increased from about 400 several years ago.
They are annoyed at the mess and the smell of droppings and feathers the birds leave on the foreshore when they roost.
But Pouto-based Logan Forrest of Whangarei's Ornithological Society says big numbers of the birds are nothing new to the Kaipara.
He believes increased rat and stoat populations brought about by several dry summers may be seeing them seeking "safer" roosts.
Toheroa populations in the past have also seen dieoffs or declines, and the dry weather may also be behind the shellfish moving with less fresh water in sand where toheroa are found.
It is easy to blame the oystercatchers, but they have been feeding on small toheroa along with many other bivalve shellfish like cockles, pipi, mussels and tuatua for a long time, Dowding says.
"It's not like they have just discovered how to do it."
The birds are taonga/treasures to southern iwi Ngai Tahu, and are also protected, Dowding says.
Serious research would be needed to get to the bottom of what's happening to the toheroa beds, which would require funding and that may be hard to come by.