Spot the difference...

Commonly confused but with quite different histories, the South Island Robin and Chatham Island Black Robin belong to the Petroicidae family which also includes Tomtits.  As the name suggests Chatham Island Black Robin are endemic to the Chatham Islands and are restricted to two islands, Rangatira and Mangere Islands. In contrast, South Island Robin are found in South Island forests north of Arthurs Pass, in Fiordland and on Stewart Island, more commonly where Stoats and Rats are controlled. 
Physically these two Robin species are very similar in size, with South Island Robin slightly heavier than their Chatham Island counterpart.  South Island Robin are a sooty black with a cream breast and the Black Robin is entirely brownish-black.  While the Black Robin has a tidy cup-like nest made from bark, moss and spiderwebs lined with feathers the South Island Robin’s nest is a scruffy collection of twigs, branches, leaves and moss surrounding a small cup-like nest built by the female. 
The Robin’s habit of feeding amongst leaf litter collecting larvae, insects, worms and spiders puts them at risk of predation by mammalian predators.  This predation is thought to be the reason for the decline, almost to the point of extinction, of the Chatham Island Black Robin.  A huge effort began in the 1980’s to bring this small songbird back from the brink of extinction when only seven birds remained. 
Old Blue, the only surviving female plus six males were transferred from Little Mangere to Mangere Island to aid conservation efforts.  Eggs laid by Old Blue were placed in Tomtits nests to boost egg production and by 2013, the Black Robin population was estimated at 250 birds.  Due to their limited genetic diversity Black Robin are vulnerable to diseases and are classified as critically endangered.
Although South Island Robin are classified as not threatened, this trusting bird is still at risk of predation by rats, stoats, possums and feral cats.  Kaipupu Point Sounds Wildlife Sanctuary is now home to the South Island Robin with 24 birds transferred on the 1st of March 2016.

Above Left: South Island Robin, image by Heather Smithers
Above Right: Chatham Island Robin, image by Dianne John