About Petroica australis longipes (Lesson & Garnot, 1827)
The South Island robin, scientifically named Petroica australis longipes (Lesson & Garnot, 1827), is a small passerine bird. It measures 10–18 cm in length and weighs approximately 35 grams. North Island robins resemble both female and juvenile South Island robins, as well as all Stewart Island robins, which can make distinguishing between the three groups difficult. Females and juveniles within the same robin group look similar to one another, though newly independent juveniles may not yet have developed their lighter-coloured breast patch. Male North Island robins are almost black, with a white spot just above the beak and a greyish-white lower breast. Females and juveniles of North Island robins are greyer, with more variable pale patches on their breasts and throats. Male South Island robins are dark grey apart from a distinct yellowish-white lower chest, while females and juveniles are lighter grey with a less distinct breast patch. Stewart Island robins of both sexes look similar to North Island robins. New Zealand robins are relatively long-lived, with wild lifespans of at least 14 years recorded. Historically, the South Island robin occupied most of the lowlands of New Zealand's South Island. Over the last century, its distribution has become far more patchy due to habitat loss and predation by introduced species. There are two populations on the South Island's east coast, and the species is slightly more common in the northern and western parts of the island. It has fared slightly better than the Stewart Island robin, which is now restricted to just 3 subpopulations, all located in Leptospermum swamp scrubland. While this is not the Stewart Island robin's preferred habitat, it has far lower populations of predatory mammals. At one point, the total Stewart Island robin population dropped below 500 individuals. A translocation programme to establish new populations on predator-free islands, including Ulva Island, Motuara Island, and Nukuwaiata Island, has proven relatively successful; around 600 individuals live on Motuara Island alone. On the South Island, P. australis shows a strong preference for Douglas fir plantations over native kanuka forests or Monterey pine plantations. This preference appears to be linked to forest structure rather than food availability or suitable nesting sites: the species favours structurally simple forests with dense, even canopies and leaf litter covering the ground. After South Island robins were introduced to Ulva Island, nesting success was positively correlated with the presence of broad-leaved coastal vegetation. South Island robins have generally responded well to pest control programmes that use aerial 1080 poison operations. These operations have led to increased chick and adult survival, and increases in population size. A 2012 study of a marked robin population, conducted by the University of Otago during a 1080 operation using cereal baits, found no negative impact on the robins and suggested that reducing predation pressure from introduced mammals would likely lead to population growth. A small number of robin deaths from accidental 1080 poisoning after pest control operations have been recorded, however. Most of these deaths occurred during four specific 1980s operations that used poor-quality carrot baits.
