Seven Unknown Islands Explored

Forest and Bird, Issue 293, 1 August 1999, Page 22

Seven Unknown Islands Explored

ical survey of seven ‘unknown’ islets lying off Waiheke Island in the Hauraki Gulf. These islets are the offshore islands of an offshore island, spray-washed, wild and relatively unknown; yet from some of them you can still glimpse the commercial skyline of Auckland City. The survey records the populations of seabirds, lizards and large invertebrates; also native vegetation, adventive weeds and the presence of rodents. (Where possible, Mike also got rid of the rats.) A further objective was to compile any human history, including traditional Maori names and their meanings, and to record the presence of archaeological sites. ‘Early on I discovered Koi Islet (0.28 hectares) lying only 250 metres offshore from the southern side of Waikeke Island, Mike Lee records. ‘It is remarkable for the species diversity it supports. ‘At least eight species of seabirds and shorebirds, including reef heron (threatened), Caspian tern (rare), variable oystercatcher (threatened), pied shag, little shag, white-front-ed terns, red-billed, and black-backed gulls were recorded breeding on Koi. In a followup visit, one year later, I observed spotted shags but it was not clear whether they also had bred there. The most numerous species were red-billed gulls and Koi appears to be their most important breeding site in the inner Gulf. The closest other significant breeding place for these birds is in the Mokohinau group, on the farthest outer limit of the gulf. ‘In all, more than 250 birds were present over the summer season on Koi. I found this tiny island a veritable biological powerhouse — not only did it support a huge amount of birdlife for such a small area, but I also found ship rats in record densities — at least 78.57 rats per hectare, which is to my knowledge one of the the highest densities recorded in New Zealand for any species of rat. These rats had been able to insert themselves into the system by displacing lizards. @ Papakohatu, or Crusoe Island (0.7 hectares), lies between Motuihe and Waiheke and has a small coastal forest. It is a breeding site for seven species of seabirds, including threatened reef heron and variable oystercatcher, though in much lesser numbers than on Koi. It also supported large numbers of mice. Lying 1200 metres from the nearest land, and now rodent free, Papakohatu has a significant conservation potential ideal, for instance, as a release-site for lizard species. @ On other trips I found reef heron breeding on Passage Rock (0.3 hectares). This shy bird generally suffers from a lack of suitable habitat for breeding, but secure offshore islets are ideal. @ Nani Islet (0.7 hectares) on the northern side of Waiheke proved to be an important breeding site for white-fronted tern. @ New Zealand dotterel regularly breed on Kahakaha (Frenchmans Cap) (0.38 hectares). @ Two islets, Motukaha (0.4 hectares) and Te Whau (0.9 hectares), contain important Maori archaeological sites. Interestingly, the pa site on Motukaha, which lies close by land at the head of Church Bay, Waiheke, had never been officially recorded or surveyed until my visit. @ During the course of my research, I was able to rediscover the old Maori name of Takapu for Passage Rock, first recorded by Dumont D’Urville in 1827 but lost from charts some time in the nineteenth century. VI ike Lee’s study, part of an MSc thesis, records the findings of an ecolog-