Tiny rock stacks around the world have critical value for conservation but are often neglected. Yesterday I visited a number of such small rock stacks in New Zealand’s Hauraki Gulf to check on their status. With a fantastic cold and clear day on a calm Hauraki Gulf, after one of the largest recorded storms in the Southern Ocean, we set out to check who was living on, and who might be visiting, some of these small islands. Landing on them can often be tricky, but once ashore all kinds of seabirds, reptiles and invertebrates might be found, some exclusively such as the Stack H stag beetle.
Unfortunately, the islands we were checking have had rats periodically visiting as far back as anyone can remember. Although the rats can’t establish a breeding population, they use these rocks as stepping stones to reach larger islands, and can still cause huge devastation on the vulnerable species living on them, such as when rats reached tiny Maria Island in the Hauraki Gulf, leading to the first ever rat eradication in New Zealand. At the moment nearby on Rotoroa Island rats have again swum over probably via one of the stacks we are checking, and the managers are launching a biosecurity response to remove the invaders. But at this time, we don’t find sign of rats on any of the small rock stacks.
Further out in the Hauraki Gulf we come across islands which have never had rats visit any more than briefly. These islands, although still tiny, remain as rich arks for species such as seabirds, with gannets and spotted shags nesting in abundance. We circumnavigate around the islands counting the birds – although the stately gannets are all out at sea feeding and breeding has finished this year, hundreds of the endearing spotted shags are still raising their young. Stranger seabirds still are to be found – one of the island caretakers gives us a red-footed booby they had just found washed ashore. Although not the same bird recently observed at a nearby gannet colony, we will take it to the museum where birds such as these are a valuable record of changing environments.
As the sun sets and the temperature plummets we speed back to the mainland after a hugely successful and rewarding day contributing to island conservation. During this time I reflect on the fact that when someone asks the perceivably simple question: “how many islands does New Zealand have”, I can only answer with another question: “what counts as an island?”