Our Changing World for Thursday 23 June 2011

Kiwi Transfer to Blumine Island

Nola Tanner ready to release a rowi into a nest box, as DoC ranger Anna Colombus closes the carry box, and forest interior on Blumine Island's main ridge (photos: A. Ballance)

Rowi is New Zealand’s rarest kiwi species, found only in the South Okarito forest in Westland. There are just 350 or so adult birds, and one third of these birds haven’t been known to breed. Last year four pairs of non-breeding rowi were moved to Blumine Island in Marlborough’s Queen Charlotte Sound to see if a new environment, much richer in invertebrate life than their original forest home, might spur them to breed. The birds settled in well, so it was decided three more pairs would be moved this year. Alison Ballance went along for the release with the Department of Conservation’s Bill Cash, Ieuan Davies, and Anna Colombus, and volunteers Nola Tanner and Sue Timpany.

Blumine Island (PDF), which is covered in both original and regenerating forest is now predator-free, after stoats and mice were eradicated.

Nearby Motuora Island in the Marlborough Sounds is also home to rowi – in this case juvenile rowi, which are hatched and raised in captivity as part of the Bank of New Zealand’s Save the Kiwi Programme ‘Operation Nest Egg’ project. Predator-free Motuora Island is used as an open air crèche, until the chicks are large enough to return to Okarito when they are about a year old.

DoC rangers Ieuan Davies and Anna Colombus radio tracking rowi from the boat, and the north side of Blumine Island, which is a scenic reserve open to the public (photos: A. Ballance)

Macquarie Island Eradication

Subantarctic Macquarie Island is politically Australian, but biogeographically it is part of New Zealand. Situated about a thousand kilometres southwest of New Zealand, this World Heritage site is home to very large colonies of penguins and elephant seals, as well as many seabirds. During the 1800s large numbers of fur seals, and later elephant seals and penguins, were killed for their oil. A number of mammals such as cats, mice, ship rats and rabbits were introduced to the island during the 1800s and were having a significant impact on the island’s vegetation and seabird populations.

To mark mid-winter, Alison Ballance rang Macquarie Island’s satellite phone to talk with Keith Springer, a New Zealander who is project manager for the large eradication project taking place this winter. Run by the Tasmanian Parks and Wildlife Service, with extra funding from the Australian Federal Government, the eradication project is using brodifacoum baits spread by helicopter, to kill the mice, rats and rabbits. A previous attempt in the winter of 2010 was abandoned after a five week delay and bad weather meant success was unlikely. This winter, however, the aerial baiting is going well, and when it is complete hunters using dogs will search the island for any surviving rabbits.

Cats were eradicated during the 1990s, and myxomatosis was used for many years to control rabbit numbers.

Binaural sound

From left to right: The KEMAR dummy standing in the anechoic chamber; inside the dummy’s head to show how binaural sound is recorded; and Mark Poletti and the array of eight speakers used to hear the binaural sound recording (images: Alan Wright)

At Industrial Research Limited in Lower Hutt, Mark Poletti is playing around with sound, and in particular is looking at the mathematics behind surround sound systems.

To show Ruth Beran some interesting sound phenomenon, he starts by showing her an anechoic chamber, a room specifically designed to minimise sound reflection which makes it appear much larger to the ear than it does to the eye.

Mark Poletti also demonstrates how binaural sound is recorded using a KEMAR (or Knowles Electronic Manikin for Acoustic Research) Manikin. The dummy has microphones fixed inside its ears, mimicking the auditory system in the human head. Binaural recordings give the impression of three-dimensional sound, as if heard live through our own ears.

To hear this 3D-sound usually requires headphones, however as Mark Poletti demonstrates by processing the recording using tailor-made algorisms, a person sitting about 1.6 metres in front of an array of eight loud speakers, can also hear the three dimensional nature of the sound.

To hear the binaural sound recorded during this interview, click here. (Note: you will need headphones to hear the 3D nature of the sound). For another example of binaural sound, click here (again you will need headphones).

Demonstration of binaural sound

Ruth demonstrates binaural sound. To hear the effect listen to this recording with headphones.