In June, my father and sister arrived in New Zealand for a few solid weeks of exploring. Together, we traversed a wide swathe of country, from the northern tip of the Coromandel Peninsula to the southern ranges of Fiordland National Park. My family are birdwatchers, so our trip was dotted with points of avian interest. We stalked wading seabirds from behind tall grasses, screeched to halts on roadsides to get a better ID on wire-perchers, scrawled sightings and impressions in the margins of our family bird book. The photos, the memories, the marginalia— together, these would suggest that the New Zealand we explored was a bird paradise, a veritable avian Eden.
The conversations we had while traveling, though, painted a very different picture. Whether we were speaking to hut wardens or cave guides, rangers or fellow trampers, any avian conversation (and there were many) turned rapidly to the sad status of New Zealand native birds. We may have seen and heard many birds in our travels, folks conceded, but it was nothing compared to what life was like before the arrival of humans on these islands.
But how can you tell? If a journey across New Zealand reveals what seems to be abundant bird life, how do you know that it’s only a fragment how things used to be? This problem— trying to figure out where we stand now in relation to the past— is a well-recognized issue in conservation science. It’s led to an increasing focus on gathering baseline data. More and more conservation-related research includes this intentional cataloguing of current conditions, specifically for comparisons in future.
But this focus on baselines is still relatively recent, which means there’s little robust data from before, say, fifty years ago. To compare today’s New Zealand with anything earlier than that, we need to glean data from sources other than conventional baseline records. For birds, points of data have been collected from a wide variety of sources— everything from the fossil record to Maori oral histories, early naturalist observations to catch numbers from hunting permits. When these dots of historical data are connected, the picture that emerges is very unlike the snapshot my family and I experienced. Native New Zealand birds, rather than flourishing, are in a state of dramatic decline.
The difference stands stark when you compare today’s world to the world captured in the beautiful words of Joseph Banks. Banks was a botanist who traveled on Captain Cook’s first NZ expeditions. On January 17, 1770, while anchored in the forest-bordered labyrinths of the Marlborough Sounds, he wrote this:
This morn I was awakd by the singing of the birds ashore from whence we are distant not a quarter of a mile, the numbers of them were certainly very great who seemd to strain their throats with emulation perhaps; their voices were certainly the most melodious wild musick I have ever heard, almost imitating small bells but with the most tuneable silver sound imaginable to which maybe the distance was no small addition.
One botanist’s impression, evocative as it is, is not enough to represent the status of New Zealand birds prior to European settlement, but other sources of baseline information confirm the fact: the avian world of 1770 has changed, and native birds are gone, or going fast. What was once a chorus of birdsong has been replaced in the 21st century by a terrible requiem of lost birds. Extinct so far: huia, moa, Haast eagles, kokako, piopio, species of wren and bellbird and fernbird and rail, plover and merganser and owl and quail. And not yet extinct, but hovering close: kaka, kea, kakapo, whio, kakariki, takahe, tomtits…the kiwi, of course. The song drags on and on.
So what happened? What caused such a dramatic change in such a short period of time? The story is often told as one of invasions.
The invasions begin with the birds themselves. Geologically speaking, New Zealand spent a long time underwater (check out “Mountain Time” for a lengthier overview). When it emerged from the sea, it was swept clean of most terrestrial inhabitants.The only creatures that could recolonize it were the ones that could reach it over a thousand miles of ocean. That meant creatures that could fly the distance— namely, birds.
These avian intrusions started a long time ago. The earliest record of birdlife in New Zealand is a 25 million year old albatross fossil (and it’s perhaps not surprising that one of the first birds to make it to the isolated island is one that is still known for massive oceanic voyages). After that, the fossil record is a bit spotty— but things really pick up starting from about 30,000 years ago, when more avian migrants arrived from the continental precursors of Australia and South America.
When these birds arrived in New Zealand, they encountered a crucial difference from their previous homes: suddenly, they were in an environment free from mammalian predators. That’s important, because predation is a strong driving force in natural selection. Avoiding getting eaten leads to the development of defensive traits, which can include anything from camouflage to predator-avoidance instincts to the ability to fly.
But in New Zealand, avoiding ground-based predation was no longer a concern. And as a result, birds lost the reproductive advantage associated with defensive traits like flight or fear. Instead, their success came from fattening up on the rich food available on the forest floor. The fatter birds were not the greatest fliers— but there was little advantage to flying, anyways, as they had no ground-based predators to elude. And so, over many generations, natural selection tilted populations towards ground-foraging, and away from flight and other defensive behaviors. The birds, once flighted invaders from distant landmasses, evolved into plump, flightless, unafraid ground dwellers. Not every bird followed this exact pattern, of course, but even the bird species that retained the ability to fly or nest in trees adapted to life in the absence of mammalian predators.
This period, when birds became adapted to their landscape, is perhaps a point when we can apply the label “native”. New Zealand had its native birds, and so they lived for millennia.
Over these millennia, invasions continued. Every so often, a population of insects or birds would arrive from the closest land, become established in New Zealand, and gradually adapt to the new set of evolutionary constraints they encountered.
But by late in the Anthropocene Era, this pattern would change. The next invaders, rather than adapting to fit their landscape, would have the ability to drastically alter the landscape to fit their needs.
These invaders are, of course, humans. The first Polynesian settlers arrived by small boats, or waka, sometime around 1200 CE. Next would come Europeans, in the wake of Captain Cook’s journeys, settling in in the 1800s. On arriving, settlers would do what humans do— they would make their homes, find their food, build their livelihoods. In doing so, they would bring about major transformations to the landscape. Without wading too deep into the values discussion here, suffice it to say that the changes were widespread and fast, accelerating with an increasing population, the import of new technologies, and more demand for more resources.
Out of all of these changes, though, one human-derived alteration to the landscape is especially noted as the death knell for native birds. Humans did not arrive in New Zealand alone— with them came a legion of new mammals just as ready to settle into new life in a new environment as the humans were. In the waka of the Polynesians came kiore rats, the very first New Zealand non-native mammalian predator. Soon enough they were joined by Norway rats from European rigs. The rats were accidental introductions, but plenty of other mammals were brought to New Zealand intentionally. Meat animals, like pigs and goats and rabbits and deer, were introduced so that they could be released into the bush and hunted later. Livestock were brought in to create dairy, meat, and wool industries. Possums provided a good source of fur; cats and dogs, a familiar sense of home. And when the burgeoning populations of rats and rabbits grew higher than expected, new mammals were introduced to try to control the problem. Stoats, weasels, and ferrets entered the scene.
Native birds did not respond well to these introductions. The birds, flightless and fearless as they often were, made easy pickings for the voracious appetites of booming rat and weasel populations. Non-predators provided a challenge for native bird survival, too— rabbits, mice, pigs, and goats would rarely eat a bird, but competed for the native birds’ food sources. Meanwhile, humans were adding to the direct and indirect impacts of the wild mammals. They hunted birds for meat and sport, and turned habitat into human habitations. As bird populations began to fall, the challenges they faced intensified. Small populations made it hard for remaining birds to find mates. As a result, populations lost genetic diversity and began encountering new stumbling blocks of inbreeding and disease. Under these myriad pressures— predation and competition, habitat loss and population fragmentation— native bird populations collapsed fast.
And that’s basically where we stand now. Since human contact in New Zealand, 56 bird species have gone extinct. Today, 77 species are listed as “threatened”, 92 are “at risk”. Only 38 native species are currently listed as “not threatened”. Meanwhile, populations of introduced mammals (be they stoats, possums, or humans) are only increasing, and with that increase comes continuation of the threats to native birds. Although many of these threats were initiated in prior centuries, this is not a historical issue— it’s current, and continuing, and crucial.
The bright note is that some progress is being made. For a number of species, future comparisons to a 2016 baseline will reveal bigger populations, greater genetic diversity, larger areas of protected and intact habitat for their use. The amount of effort going into protecting and rehabilitating these populations is incredible— thousands of predator traps dot the country, millions of dollars are used to purchase poisons that are applied aerially to target introduced predators, hundreds of governmental and non-governmental organizations work to aid the survival of native birds and educate the public on their status. The success stories are encouraging— the kakapo population of 123 adults increased by 34 chicks this year! More offshore islands are becoming predator-free! Twelve bird taxa were moved off the “threatened” list since 2008!— but tempered by the realization that much of this is already out of our control, that many species are already lost or declining past some survival threshhold, that the current threats are unlikely to abruptly stop anytime soon, that the effects of climate change are soon going to add an entirely new layer of survival challenges to native birds.
Still, the work continues. I’m reminded of a talk I’d heard on my first trip to Fiordland. The speaker was a Department of Conservation warden stationed in the Hollyford Valley. When he first became a warden, nearly 20 years ago, he found the valley empty of birds. Distraught, he started campaigning for just one predator trap— and installed and monitored more and more traps as his cause gained attention. Over the course of twenty years, he had installed traps all along a wide and long stretch of the valley— and over that time, started to hear more and more birdsong.
The dream, of course, is unimaginable chorusing, birds singing loud and raucous in the trees, a bird book covered thick with sighting notes for every species. A new baseline.
Until next time,
Conservation status of New Zealand birds, 2012 by Hugh Robertson, John Dowding, Graeme Elliott, Rod Hitchmough, Colin Miskelly, Colin O’Donnell, Ralph Powlesland, Paul Sagar, Paul Scofield, Graeme Taylor 2013. New Zealand Threat Classification Series 4.
(Unless otherwise noted, all photos are author’s own.)