DOC has recently completed an annual flock count for the critically endangered southern New Zealand dotterel/tūturiwhatu and found an estimated 101 birds remain – a 19 per cent decline from last year's 126.
DOC Ranger Daniel Cocker says the numbers highlight the precarious position this population is in, despite continued predator control efforts.
"Southern dotterels, which only breed on Stewart Island/Rakiura, have spent the past few decades on the brink of extinction and sadly this year looks to be a similar story," says Daniel.
"Without our control efforts, it's frightening to think just how low the numbers would be."
Dotterels face a range of threats, but the number one cause of decline is predation by feral cats. During the recent breeding season, 32 feral cats were killed by the team across the breeding sites.
"Adult dotterels will actively defend nests and chicks, making them easy targets for predators. Dotterels are also curious and easily approached.
"We believe at least 41 adult birds died over the 2023 breeding season. This was partially offset by this year's surviving chicks, meaning an estimated population reduction of 25 birds."
Following this year's flock counts, the team will review predator control strategies as part of an adaptive management programme.
The challenge is feral cats roam large distances and can be wary of the traditional methods to control them – trapping, hunting and bait stations. There are limited tools to control feral cats across large areas.
Predator control is only undertaken on a portion of dotterel breeding habitat which is patchy and extends across the full length of Rakiura. To save more dotterels, more habitat needs to be protected.
Long term solutions require landscape scale change – this is why initiatives such as Predator Free Rakiura, which aims to remove possums, rats, feral cats and hedgehogs from the island, are so important. In the meantime, the focus is on effective predator control to hold the line and prevent extinction.
Despite this year's low numbers, the team remains hopeful for a turnaround in the dotterels' fortunes.
"In 1992, the population reached an all-time low of 62 birds but bounced back to 290 birds in 2009. Given the right conditions, dotterels can be very resilient, and produce multiple chicks per year."
The New Zealand Nature Fund is supporting DOC's campaign to save the southern dotterel and has raised over $62,000 from private donors in the past six months.
"Southern dotterels were once widespread throughout the South Island and Rakiura is their last refuge. It is an uphill battle but it's one worth pursuing."
Background information
Southern New Zealand dotterels (SNZD) were once widespread throughout the South Island, breeding in the high country, and have been recorded as high as 2,500 metres above sea level. They disappeared from mainland breeding sites by the early 1900s due to introduced predators and human hunting. Rakiura remains their last refuge where they face threats from feral cats and even white-tailed deer which have been caught on nest cameras eating eggs. Spur-winged plovers, Australasian harriers and black-backed gulls are also believed to pose a threat to dotterels.
The only place you can reliably see a SNZD on the South Island mainland is at Awarua Bay near the Tiwai Aluminium smelter. Awarua Bay is a key site where a third of the population feed and flock together for most of the year before returning to the mountain tops of Stewart Island/Rakiura to breed. They also congregate at Mason Bay during high tides.
Differences between southern and northern dotterels
Southern dotterels are recognised in New Zealand as their own sub-species but by the IUCN (International Union for Conservation of Nature) as a separate species. They differ from the northern dotterels in both behaviour and appearance. While southern dotterels breed on mountain tops, the northern birds breed on beaches around the North Island coastline.
Southern birds are larger and darker in breeding colours than northern birds. They also have a larger mid-toe which is believed to be used for better stability in the alpine environment.
There are estimated to be more than 2,500 northern dotterels (conservation status: 'recovering').
The conservation status of the southern dotterel remains 'nationally critical'.
