The first chick of the Southern New Zealand Dotterel breeding season was spotted by Department of Conservation (DoC) rangers last week.

The critically endangered birds are known to nest only on Rocky Mountain on Rakiura Stewart Island where they breed above the bush line among alpine plants and scrub. The new chick sighting has confirmed the existence of at least two active nesting sites in the area.

In April 2022 the population was estimated at 144 birds, but this number has fallen sharply with an estimated number of just 126 (April 2023) - a decline of 13 per cent.

The birds are extremely vulnerable to predation, mostly by feral cats and from mustelids (stoats, weasels and ferrets) during their feeding forays to Awarua Bay near Bluff during the winter months.

A pair of Southern Dotterels on Rocky Mountain during the current breeding season. Photo / Daniel Cocker, DoC

Four permanent dotterel rangers live on the island undertaking predator control and making an annual census of the birds. They step up the feral cat control in nesting areas in preparation for the breeding season, which runs from October to early January.

Cat numbers, however, have boomed in recent years as they have feasted on a surge in rat numbers following a mast or heavy fruiting year. Cats prefer rats and they thrive when rats are plentiful, making life even more precarious for dotterels who are threatened not just by the cats, but also by possums and even white-tailed deer who have been filmed eating dotterel eggs.

The shy and hard-to-spot dotterels nearly disappeared completely 30 years ago. In 1991 there were only 66 known birds. Effective pest control saw the numbers blossom to around 300 birds in 2010, but they have been in steady decline ever since.

The new chick sighting is encouraging; it has incubated for 30 days and will fledge after about six weeks when, it is hoped it will feed in the estuaries and beaches of Southland on invertebrates, crabs and crustacea before heading back up the mountain next October for the next breeding season. And maybe have chicks of its own.