People who've worked to save toheroa beds on Northland's west coast say the Department of Conservation should cull the native birds that are eating them.
Locals living near Ripiro Beach in Kaipara said pied oystercatchersoyster-catchers had learned how to dig for young toheroa, and were destroying entire beds.
Ornithologists have expressed scepticism, but some locals said the birds get their strong beaks into the tube which toheroa extend to the surface of low-water sand and suck the mollusc from its shell.
An Uri o Hau leader, Mikaera Miru, said years of effort have gone into seeding the shellfish and planting dunes on the beach to create an ecosystem that will nurture them.
He said it was gut-wrenching to see what is taking place, and culling the small flock that was doing the damage appeared to be the only answer.
The birds were legally hunted until the Second World War.
Mr Miru said pied oyster catchers were plentiful - but toheroa are not.
And a Northland fisheries officer said that if toheroa beds were vanishing from the Kaipara coast, there was no evidence that human predation was a key factor.
The district compliance manager, Steve Rudsdale, said officers did catch people taking the protected shellfish - but not many.
Mr Rudsdale said the only legal way to take toheroa was with a customary permit, but iwi these days gave out very few.
The South Island pied oyster-catcher is the nation's most abundant oyster-catcher, and they're noted for having survived threats such as the introduction of mammalian predators.
In coastal areas, they feed mainly on molluscs and worms, and have a strongly developed behaviour for preying on bivalve shellfish, though they can also eat crustaceans, and fish.