Greatest recovery by a bird species

The Chatham Island robin, also called black robin (Petroica traversi) – endemic to New Zealand's Chatham Islands in the South Pacific – came very close to extinction in the late 20th century. In 1972, only 18 individuals could be found in the wild, dropping to seven by 1976 and a mere five by 1980. Of these five, there was only one female (named “Old Blue”) whose partner was a male called “Old Yellow”. With the help of local wildlife protection officers and an innovative conservation technique of “cross-fostering” where the robins’ eggs and hatchlings were given to similar bird species to brood and raise, in order to increase the number of individuals, the black robin was able to experience a staggering comeback. As of the last census conducted in October–November 2015, a total of 289 adult black robins were counted (246 on Rangatira Island and 43 on Mangere Island).

All of today’s black robins are descended from “Old Blue”; having reached 14 years old, she is one of the oldest specimens of Chatham Island robin on record.

The reason that Chatham Island robin numbers plummeted was the introduction of predators, such as rats and cats, to their native islands. Given their shared genetic heritage, this endangered species is still under the threat of a disease, which could be catastrophic.

Another species to have made a similar back-from-the-brink comeback is the endemic Mauritius kestrel (Falco punctatus), which also suffered in the 20th century due to introduced alien species and the use of harmful insecticides in agriculture. By 1974, its population had been reduced to just four individuals in the wild and two individuals in captivity (making it, some suggested, the world’s rarest bird at the time). By 2013, it was estimated their population had increased to 350–500 individuals with around 85–100 breeding pairs.