Down to just one breeding pair 40 years ago, the bird bounced back after extraordinary efforts – now its survival is again under threat

Forty years ago, on a remote rocky island in the Pacific, 800km east of New Zealand, a conservationist set out to bring the rarest bird in the world back from the brink of extinction.

Don Merton, wearing a check shirt and shorts, climbed 200 metres up the rockface of Little Mangere Island, part of the Chatham Islands (Rēkohu in the indigenous Moriori language and Wharekauri in Māori), and laid a soft netted trap for the black robin, also known as kakaruia and karure – a tiny endemic bird that lives up to its name, with black plumage, black eyes and a little pointy black beak. Once captured, he gently placed the bird inside a wooden box, strapped it to his back, descended the cliff and jumped on a boat to the neighbouring island – Mangere, a larger, more verdant habitat.