by Alison McDonald, DOC Ranger
New Zealand’s periphery is dotted with small out-lying islands, and while it might seem logical to think of these as extensions to the mainland or mere microcosms of the familiar – the reality is that these places, isolated only by a small expanse of sea, offer us a glimpse into a different dimension.
Whakau or Red Mercury Island sits tantalisingly close to the mainland – just a ten-minute helicopter flight from the Coromandel coast – yet much of what is found there is distinctly different to what is found on the nearby peninsula. For a 225 hectare rocky outcrop the island boasts a surprising diversity of habitats. To date over 500 separate species of plants, invertebrates, reptiles and birds have been recorded here, a small number of which are unique to the Mercury Islands group.
Fortunately for the native wildlife of Whakau, only one introduced mammal was ever released onto the island – a small Polynesian rat, known as the kiore. This was successfully eradicated in 1992 and since then, life has flourished pretty well on its own, enhanced only by a small number of species re-introductions and minimal weed management.
In October 2018, in an effort to record the success (or otherwise) of the plants, birds, reptiles and insects residing on the island, a small team of DOC staff and volunteers – including Steve Bolton, Rob Chappell, Peter Corson, James Russel, Jo Peace and Ian Stringer – decided to pay a visit. Over four successive days the team dispatched themselves across different pockets of the forest-clad landscape placing tracking tunnels, setting pitfalls traps and counting bird calls, often starting before first light and working well into the night to capture the full spectrum of species in action.
A typical day on the island starts somewhere around 4 am with a dawn chorus like no other, as various species of seabirds, including petrels and shearwaters, stumble from their forest burrows, to find a convenient launching platform. As they do so, they call to one-another, issuing forth a chorus of shrill whistles and cat-like wails.
Just as the noise of the sea-going birds begins to fade away, the land birds take centre stage. What begins as a few lonely notes echoing in the still-dark morning, builds to a cacophony of robust trills, musical whistles and rhythmic chatterings – the customary sound of riroriro, pīwakawaka and korimako mixing with the less-familiar kākāriki, tīeke and kākā.
As the sun continues to rise a variety of additional creatures become active across the island – copper skinks can be seen scuttling over scrub and rocky boulders near the coast, while industrious native insects and spiders – some entirely unique to these islands – busy themselves in their daily quest for food and survival.
Night time is no-less busy for the residents of Whakau. For tuatara, tusked-wētā as well as multiple nocturnal skinks and geckos, this is prime-time – they emerge from their respective day-time burrows or crevices and lurk ominously in the darkness, poised for any hunting opportunities which might present themselves. Ruru call mournfully from unseen perches in the canopy and little-spotted kiwi declaim their territory with high-pitched trills which resonate across the island.
In the absence of any pests and with minimal disturbance, it seems the wildlife of Whakau is beginning to prosper. In their limited time on the island the research team confirmed that all species of birds and invertebrates intended to be used a source-populations for near-future translocations were sufficiently robust. That said, ecosystems restoration is a long, slow process and it will likely be many more decades before all habitats have fully replenished themselves and all species can be considered safe.
But the good news is, we’re moving in the right direction. And with ambitious conservation projects continuing across New Zealand, we can expect to witness more of this island magic on the mainland in the years to come.