Island transformation - Burgess Island research trip - Sept-Oct 2016
NNZST trustee Chris Gaskin has been visiting Burgess Island (Pokohinu) in the Mokohinau Island group in the outer Hauraki Gulf since 2004 and has seen some remarkable changes in those 12 years. The western Mokohinau Islands were amongst the first islands subject to aerial poison drops to eradicate mammalian predators - in this case Pacific rats in 1990. The transformation of Burgess has been amazing to witness with seabirds, land birds and reptiles all rebounding. There are now seven species of ‘petrels’ breeding on the island (grey-faced petrel, black-winged petrel, white-faced storm-petrel, fluttering shearwater, little shearwater, sooty shearwater and common diving petrel) – prior to eradication there were only one or two with others possibly trying to breed but the rats would have eaten them out.
But there’s another transformation that happens with islands like Burgess – it’s the nature of many ‘seabird islands’ - those with species that are nocturnal over land. The only time seabirds come to land is when they breed.
During the day kakariki, bellbirds, tui, fantails, NZ kingfishers and the occasional pigeon make this formerly grazed island with its rank grass, drifts of muehlenbeckia, and regenerating shrubs and trees their home. Red-billed gulls and pied shags cruise the coast. And while shearwaters, fairy prions, diving petrels and storm-petrels are seen close to shore during the day feeding in the productive waters of the outer Gulf, it is at night this fabulous seabird island really comes to life.
Chris’s latest visit, part of a research team led by Dr Matt Rayner (Auckland Museum) with Dr Todd Landers (Auckland Council), PhD student Rachael Sagar and the newly ‘anointed’ Dr Jingjing Zhang (both from University of Auckland) focussed on three species – common diving petrel, little blue penguin and white-faced storm-petrel – three separate projects investigating the birds’ physiology, their foraging (a joint project with University of Auckland's Dr Brendon Dunphy who was on Tiritiri Matangi at the same time) and, in the case of storm-petrels, their migration post-breeding (a twinning project with Nicholas Carlile in Australia) and also, it transpired, their fidelity to previous nest sites.
The nights spent on the northern part of the island was a chance to marvel at the transformation that takes place after the sun sets. First the calls of penguins swimming under the great cliffs on their way to landing points around the coast. Then grey-faced petrels, their high-pitched and ‘oi’ calls heard, then seen, dark ghosts skimming back and forth across the cliff tops and slopes. Soon after dark is when the real action begins as thousands of storm-petrels drift across the slopes. The video here captures something of this remarkable scene – each night, calm or in gale force winds, clear skies or pouring rain. These tiny 40-50g birds had just returned from their migration to the eastern Pacific – returning to old burrows, to make new ones, to mate, the start of a breeding cycle that will last through to February.
There will be many more visits to the island – tracking the changes that are taking place and studying the lives of these remarkable creatures.