After human intervention stopped, rim laying became less frequent, but 9% of birds still laid rim eggs as of 2011. Humans stopped pushing eggs back in time to prevent the gene spreading to all birds which could have made the birds dependent on humans indefinitely. The maladaptive gene causing this behaviour spread until over 50% of females laid rim eggs. Human conservationists pushed the eggs back into the nests where they were incubated and hatched successfully. Many females laid eggs on the rims of nests where the eggs could not survive without help. The tomtits raised the first brood, and the black robins, having lost their eggs, relaid and raised another brood. The team increased the annual output of Old Blue (and later other females) by removing the first clutch every year and placing the eggs in the nest of the Chatham race of the tomtit, a technique known as cross-fostering. The remaining birds were moved to Mangere Island. They were saved from extinction by Don Merton and his Wildlife Service team, and by 'Old Blue', the last remaining fertile female. There are now around 250 black robins, but in 1980 only five survived on Little Mangere Island. They frequent woody vegetation under the canopies of trees such as akeake. To shelter from the strong winds and rough seas around the islands, they spend a lot of time in the lower branches of the forest, or in flat areas with deep litter layers.

They are entirely insectivorous, feeding on the forest floor or on low branches, and preferring to nest in hollow trees and tree stumps. Black robins live in low-altitude scrub forest remnants.

Black Horse River by Robin Studwick