The Auckland Islands shag is a medium-sized, black-and-white cormorant with a short black crest. The black plumage of the upperparts glitters with a metallic blue sheen and contrasts starkly with the white of the underparts and throat and pink of the legs and feet (4). The upperparts and wings may be wholly black or with some white on the wings, appearing as a bar when folded, and some males have a white patch on the back (2)(4). During courtship displays, the male barks and makes ticking sounds, while the female gives a soft purr (4).
The Auckland Islands shag nests in colonies, with females usually laying a clutch of three eggs between November and February, followed by an incubation period of around 28 to 32 days (2)(3). However, a brood of only two chicks is normally successfully raised (2).
This marine bird forages both in open sea and in sheltered coastal waters, and breeds and roosts on ledges, on the tops of sea cliffs, in hollows, and also sometimes on flat ground amongst grass tussock or in the shelter of overhanging rocks, bushes or trees (2).
Since pigs on Auckland Island destroy any colonies they can reach, colonies have been largely restricted to inaccessible sites. Before they were removed, cattle and rabbits had a similar impact on Rose and Enderby and, on Enderby, cattle have wiped out a tussock grass that was a preferred nesting material. Cats are another potential predator on Auckland Island and pose a threat to this native bird (4). Additionally, nests have sometimes been washed away by high tides and storm waves (2).
In 1993, feral cattle and rabbits were removed from Enderby and Rose and, in 1995, feral goats were eradicated from Auckland Island. The Auckland Island group has long been a nature reserve and, in 1998, was declared part of a World Heritage Site. In 2003, the area was further designated a Marine Reserve (4).
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