South Island Robin

Historically, the South Island robin inhabited much of the lowland of New Zealand's South Island, but its distribution has become much more patchy in the last century due to habitat loss and introduced predation. There are two populations on the east coast of the South Island, and they are slightly more common in the north and west. It has fared slightly better than the Stewart Island robin, which has been relegated to 3 subpopulations, all of which are in Leptospermum swamp scrubland—although this is not their preferred habitat, it is less heavily populated by mammalian predators. Total population was lower than 500 individuals at one point. A programme of translocation to predator-free islands (such as Ulva Island, Motuara Island, and Nukuwaiata Island) was instituted and proved relatively successful at establishing new populations (around 600 individuals on Motuara alone). In the South Island, P. australis has a strong affinity for Douglas fir plantations, instead of the native forests (kanuka trees) or Monterey pine plantations. This is apparently due to forest structure rather than strict food availability or viable nesting sites, as the species prefers structurally simple forests with dense, even canopies, and ground covered with leaf litter. When the population was introduced to Ulva Island, nesting was positively correlated with the presence of broad-leaved coastal vegetation.

The South Island robin is listed as being of least concern on the IUCN Red List. However, the Stewart Island robin (Petroica australis rakiura) has gone through a couple of bottlenecked populations recently because of deforestation and habitat loss, as well as introduced predators, such as rats, stoats, and feral cats. Because of this sharp decline in the Stewart Island population, several attempts have been made to translocate the Stewart Island robin to other islands nearby where introduced predators do not exist or have been eradicated (see above). However, many of these translocations have involved 12 or fewer colonising individuals, making inbreeding nearly unavoidable. This has led to some apparent immunocompetency issues as well as reproduction problems. On Motuara Island, high rates of hatching failure as well as fewer clutches were observed. Inbreeding and its genetic and immunological consequences, therefore, remain a concern with this subspecies. In contrast, birds in the South Island do not show much genetic loss in comparison with historical populations, although their distribution on the island has become increasingly fragmented.