Twenty whio [blue duck] have been released on the West Coast, boosting the population of the bird that is rarer than some species of kiwi.
It comes after the Central Southern Alps Whio Security Site, where the whio live, extended to the Big Wainihinihi River after additional predator traps were added due to the risk of stoats preying on young and nesting whio.
Whio were also released today on the Kawhaka River, and the Styx and Arahura Rivers.
Nicole Kunzmann of the Department of Conservation's Hokitika branch said breeding assistance from the Whio Forever programme has helped to increase the population from 298 pairs in 2011 to 652.
"We recently surveyed the Big Wainihinihi and were only able to find one male duck, which we think may recently have lost his mate. Hopefully the newly released whio will pair up, establish territories and breed in the years to come."
Karen Sky, Genesis Energy's Environmental Manager who is part of the Whio Forever project team, said the chance of encountering whio "in our backcountry is increasing with every release that takes place".