Several rare birds are dead in Canterbury after people in four-wheel-drive vehicles and on motorbikes rode through a colony of nesting black-billed gulls.
The drivers killed 10 birds last week in the Ashley Rakahuri Regional Park just north of Christchurch, which Environment Canterbury chairperson Jenny Hughey calls "extremely disappointing".
"These beautiful birds are unique to New Zealand, mainly breeding on South Island braided rivers, are 'nationally critical' and rapidly declining, and are the most threatened gull species in the world," she says.
With current trends, the population of black-billed gulls would decline around 70 percent over the next 30 years, Hughey says, but luckily the birds have had a successful breeding season and the Ashley Rakahuri Rivercare Group and local community have been working to keep the birds safe.
"We monitor the area closely, and there is signage installed along the river advising park users about the nesting area, and concrete blocks are installed at entry points to deter vehicles," she says.
"The measures we, and the Ashley Rakahuri Rivercare Group, have taken this season have been largely successful and the majority of park users have been respectful and avoided this area."
The black-billed gulls' nesting areas are protected by the Wildlife Act, which is administered by the Department of Conservation. These areas have been cordoned off since September to protect the colony and will open in two weeks when the birds have fledged.
Environment Canterbury is currently exploring what its enforcement options are, Hughey adds.
Grant Davey, a member of the Ashley Rakahuri Rivercare Group, says this year they've had the second-largest black-billed gull colony on the river in 20 years.
"The 1278 nests have produced approximately the same number of fledglings (flying chicks) - this is a very good outcome," he says.
But he says the people who drove through the colony showed "reckless" behaviour.
"In one case a 4WD was seen to speed up when approaching the birds."
He adds there are also much more vulnerable smaller chicks as well as black-fronted tern and banded dotterel chicks in the area.
"Environment Canterbury and the Ashley Rakahuri Rivercare Group have done a lot of work through education, publicity and the installation of signs and physical barriers to stop vehicles getting on the river - this sort of thing should not still be happening," he says.
"People should be aware that killing protected native wildlife can result in penalties of up to $100,000 in fines and two years in prison. Black-billed gulls have a conservation status of nationally critical."
Kingsley Timpson, operations manager of the Department of Conservation's Rangiora office in North Canterbury, said it was "unacceptable for people to drive through colonies of this threatened bird" and said the department would be looking into reports of vehicles driving in the area.
If anyone sees people disturbing these colonies, they can contact Environment Canterbury on 0800 324 636.