Chatham Island black robin  (Petroica traversi)

The introduction of mammalian predators such as rats and cats to the Chatham Islands, following European settlement, caused a rapid and deleterious decline in black robin numbers; the species became extinct on all but one island (6). By 1880, the species was restricted to around ten hectares of woody vegetation on a mammal-free rock-stack known as Little Mangere Island (4). Habitat loss on this island further threatened the species however, and prompted an intensive conservation programme that began in the 1970s (4). Today a population of around 250 to 300 birds exists on two small islands: Mangere and Rangatira (or South East) Islands (6). Although all are descended from just one pair and are genetically identical, there are no apparent deleterious effects resulting from their small gene pool (6). The possibility of accidental predator introduction remains a threat (2).

In the 1970s, habitat loss on Little Mangere Island was so severe that the population of seven birds was moved to Mangere Island. By 1980 however, the situation had reached crisis point with only five birds left in the world, including only a single breeding pair (4). The New Zealand Wildlife Service began 'cross-fostering' eggs and young from this remaining pair of robins (known as 'old blue' and 'old yellow') to another species in an effort to increase productivity (5) (4). This innovative approach was a resounding success; today between 250 and 300 birds are distributed on Mangere and Rangatira Islands and there are plans to introduce a population to the much larger Pitt Island once it has been cleared of pests (5) (6). This is a remarkable conservation success story and an example of what can be achieved (4).