Bringing species back, New Zealand style

A recently ringed male hihi

Male hihi  (photo credit: Leila Walker)

In the heart of New Zealand’s Waikato region, rising out of a sea of gently rolling pastoral farmland, is an imposing remnant of ancient forest that draws you in. Maungatautari Mountain. In many ways, this 34 km2 rugged pocket of land reflects the story of New Zealand as a whole: an isolated landmass brimming with uniquely wonderful life, now engaged in a spirited fight back after introduced pests threatened the existence of native flora and fauna. Central to this resurgence is New Zealand’s pioneering use of pest eradication and native species reintroduction.

In this, Maungatautari is leading the way. The world’s longest pest-proof fence stretches for 47 km around the mountain’s perimeter. Completed in 2006, it has ensured the eradication of all mammalian pests, with the exception of mice. The exclusion of the likes of cats, rats, mustelids and possums – to name just a few of the offenders – has paved the way for the reintroduction of a rich variety of native wildlife long missing from Maungatautari’s slopes.

An ancient forest sanctuary

Were you to venture out onto Maungatautari today, you stand a chance of encountering kiwi, the nation’s flightless feathered icon, or hearing the haunting song of the kokako, a slate grey bird with deep blue wattles and a tendency to bound from branch to branch through the forest canopy. Perhaps more likely, you might be terrorised by kaka, an energetic parrot threatening to collide with you as it tears through the forest flashing a red underwing and emitting a prehistoric-sounding caw. Birds aside, you might stumble upon tuatara, a spiny-backed reptilian endemic and the sole survivor of the order Sphenodonita, or Mahoenui giant weta, a giant insect weighing up to 35 grams and harking from the time of the dinosaurs.

Recently, I did have the good fortune of exploring Maungatautari’s slopes. I was intent on tracking down hihi, one of New Zealand’s more colourful birds. Their Māori name, meaning ‘ray of sunshine’, refers to the striking yellow plumage of males. Unfortunately, hihi are in need of help. Like so many other New Zealand endemics, the future prospects of this particular species are very much dependent on the success of reintroductions. Originally found throughout the North Island, by the late 19th century hihi were precariously restricted to just one offshore island. Now, thanks to a series of reintroductions beginning in the 1980s, an additional five populations exist, Maungatautari among them.

Hihi on the Maunga

Hihi were first reintroduced to Maungatautari back in 2009, with a couple of top-up reintroductions in 2010 and 2011. A crucial component of measuring the success of reintroductions is conducting post-release monitoring. Without closely following the fortunes of a newly established population, over successive years, it is impossible to know whether the reintroduction can be counted as a success. And Maungatautari’s size and terrain, coupled with the fact that few hihi visit supplementary feeding stations, and none use nest boxes, presents no small monitoring challenge.

I happily, and perhaps a little naively, took up the monitoring challenge this season. My goal, in the time available before breeding commenced, was to search the mountain’s many ridges and gullies for hihi, catching and counting as I went. The extensive network of pest monitoring lines that criss-cross the mountain’s forested expanse certainly made the going easier. They did not, unfortunately, spare me numerous humiliating experiences. On any given day out on Maungatautari, I could invariably be found engaged in serious fieldwork: sliding inelegantly down muddy slopes on my behind, slipping face first into a slimy bed of parataniwha, loosing my footing on moss-covered steam beds, tripping on concealed tree roots, being poked in the eye by the spindly point of a mingimingi shrub or becoming entangled in a dense knot of supplejack vines. The forest, I feared, seemed to be telling this mammal that I didn’t belong. Hihi, we rather hope, do belong in this forest. An abundance of natural cavities for nesting, and a wealth of wet gullies with dense understories that the birds seem to favour, suggests this could be ideal habitat for them.

When I do track down a hihi, I first check for the tell-tale sign that someone has seen it before: an assortment of colourful rings on its dark brown legs. If present, I record the ring combination and continue on my way. If absent, I endeavour to catch the bird using a mist net. Once lured, using playback, into this fine mesh net strung between two aluminium poles, I ring the bird with its unique combination of colours and add it to the running total. Whilst in my hand, I take the opportunity to record additional information that has, over the years, helped researchers better understand the species. Measuring ear tuft length, for example, has given us insights into the evolution of sexually selected traits, whilst noting the colour of the alula feather can helpfully be used to age the bird.

A ray of hope for New Zealand’s ray of sunshine?

Hihi are a fascinating species, and a wealth of research has sought both to discover more about the species in its own right, and inform thought in fields as diverse as evolutionary biology, parasite ecology and reintroduction biology. For example, recent research by members of the Hihi Recovery Group has variously revealed the importance of un-paired floater males for maintaining genetic diversity, the capacity of supplementary feeding to buffer the impacts of climate change, and the relationship between a bird’s temperament and the distance it disperses from birthplace to breeding territory.

As for the hihi on Maungatautari, how did they fare this season? The final tally stands at 39 birds. Compared to counts of around 50 birds in the previous two seasons, this may justify some cause for concern. Certainly, without on-going monitoring work like this we would be in the dark as to the changing fortunes of this, and other, hihi populations. Hihi may not be out of the woods yet, but the continued vigilance of a committed group of supporters ensures that the bird at least has a shot at enjoying a stable future in New Zealand’s forests.

Leila Walker
@leilakwalker

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