by Darryl Jones
And that was only Act 1 in the unfolding tragedy of Aotearoa. The arrival of the first Europeans, possibly starting with the very first ship in 1769, was to dramatically accelerate the changes already under way. The steel axes, fire-making flints, and muskets and especially the Euro-centric perspectives of the white-skinned colonists soon transformed the appearance of the countryside. Again, however, it was the intentional and accidental mammalian introductions by the Europeans that were to have truly catastrophic outcomes for the birds of New Zealand. The House Mice, Norway Rats, and Ship (Black) Rats would have simply jumped ship, as normal, while some domesticated pigs, dogs, goats, sheep, horses, and cats probably escaped from farms and homesteads to start feral populations in the wild.12 Thus has been the outcome of virtually every European colonial endeavor around the world.13
What has been especially noteworthy about the New Zealand example was the ambitious and imaginative range of species intentionally introduced for a variety of dubious reasons. While not all have survived (and ignoring over thirty species of foreign birds now established), New Zealand is now home to 34 mammals from elsewhere, from Himalayan Tahr and elk to hedgehogs and hares.14 For our present purposes, however, it is those that have taken to eating birds that are most important: the rodents (House Mouse, Ship Rat, Norway Rat, as well as the Kiore), cats (domestic pets now feral) the mustelids (ferret, stoat, and weasel) and, perhaps surprisingly, the Australian Brushtail Possum. The latter, introduced to establish a felt industry for hats, have proved to have a major impact on eggs and nestlings.15 All are ferocious predators, though two, rats and stoats, appear to be particularly effective, and widespread, even swim-ming freezing seas to reach certain islands.
The result of all these influences has been a biodiversity in free fall. Because these events have been so recent in New Zealand, it has been possible to date the disappearance of each species lost over the past couple of centuries with horrible precision. A recent book covering the extinctions of New Zealand’s birds provides an alarming graph of the stepwise disappearance of each species, shockingly arresting in its precision and finality.16 From the original 223 species known to be present prior to the arrival of humans, an abrupt plunge downward with the arrival of the Polynesians, the notation stating baldly, “All moa, geese, Adzebills and Haast’s Eagle [disappear].” Twelve species gone. The downward steps continue, gradually becoming a smoother curve declining increasingly steeply from about 1800, the labels now thickly clustered and unrelenting, starkly document-ing annihilation: North Island Kākā (1851), Hutton’s Rail (1893), Laughing Owl (1914), Bush Wren (1972). Unique species, gone forever, and many others on the same trajectory. Yet it seems that the bitter reality of this predicament—the very real possibility that even more of their precious animals could yet disappear—has transformed many New Zealanders into some of the most imaginative, innovative, and resourceful conservation biologists and managers on this planet. Facing extinction daily seems to have focused the mind and steeled their resolve; finding, slowing, and stopping the mammalian predators was paramount.
While the traditional approaches of trapping and poisoning have been significantly enhanced and fine-tuned (fortuitously assisted by the lack of native mammals), it soon became evident that eradicating these pests was simply an impossibility in such a large country with extremely challenging terrain and a human population of only about 4 million. One solution was to keep the predators away from the birds by physical separation. New Zealand has an abundance of islands just offshore, and the rather obvious idea of taking vulnerable birds to these places was tried as early as 1895. In a remarkably prescient and risky exercise for the day, a large number of birds were captured and released on islands in Dusky Sound at the bottom of the South Island in a desperate attempt to secure populations threatened by predators.17 Unfortunately, this farsighted venture failed when stoats reached the islands only a few years later. This approach was, however, revisited around the 1970s as methods of detection and control of mammals became far more effective. Although it took some time to perfect, the ability to actually remove all unwanted species from an entire island meant that the New Zealand Wildlife Service (subsequently the Department of Conservation (DoC)) was able to return to serious island translocations. DoC’s skills at removing every last possum, stoat, and rat and restoring the original vegetation rejuvenated the country’s desperate interest—and hope—in saving their precious birds. By the 1980s, this “island sanctuary” approach was to become a mainstay for the conservation of New Zealand’s birds. Today, numerous islands dotted all around the country have thriving and healthy populations of many iconic species.18 For obvious reasons, access to most of these critically important island reserves is highly restricted, and many are remote and inhospitable. There is, however, one major exception.
Visiting a Real Ark
To get to the island of Tiritiri Matangi, you don’t need to wait 3 weeks for a special DoC temporary visitors permit, arrange to be accompanied by a ranger, hire a helicopter, and come prepared for possible blizzards or ice storms. Instead, you can wander down to the harbor terminal in the Auckland CBD and catch the daily ferry. The brief voyage provides spectacular views of the city towers and the sails of hundreds of yachts against the massive glowering cone of Rangitoto, the supposedly dormant volca-nic island only 8 kilometers from New Zealand’s largest city. I went one startlingly bright day in December.
Directly ahead, the island is coming into view, its dark green forests contrasting with the white sandy beaches lining the shore. I am on my way to Tiritiri Matangi to see for myself some of the results of the extraordinary results New Zealanders have achieved in saving their birds, and to learn more about the role that supplementary feeding has played in these programs. The provision of additional food plays a major role in conservation and wildlife management plans throughout the world, used for a vast number of species and situations.19 Describing the diversity of these programs is well beyond the scope of this book. Because of the depth of research associated with these activities, however, there is much that we can learn that may be of interest and value to bird feeders in more domestic circumstances. Are there lessons from well-studied examples of applied supplementary feeding for conservation and management that might inform garden feeding?
My guide is Josie Galbraith, a colleague who has been researching bird feeding in the suburbs of northern Auckland, just visible behind the ferry in the sparkling sunlight. As well as an accomplished researcher in her own right, Josie is the ideal companion to have on this trip to Tiritiri as she spent much of her life visiting the place. “Multiple times every year, since before I was born,” she claims. Her father, Mel Galbraith, an ecologist from Unitec in Auckland, was directly involved from the earliest days in the complete transformation of the island from overgrazed rocky sheep paddock to vibrant restoration of the original New Zealand landscape. When the restoration work started in the early 1980s, only 6% of the 220 hectare (540 acre) island was covered in trees. Today, after the establishment of almost 300,000 trees, 60% is now forested, with the remainder intentionally maintained as open grassland.20 Since toddlerhood, Josie has been helping in the huge amount of digging, planting, weeding, trapping, and all the other exhausting practical tasks necessary for the restoration of a complex ecosystem. “An army of very hard-working volunteers spent years, usually over their weekends, doing all the work,” explains Josie. “I still think it was a remarkable effort by these people because no one really knew whether it would actually work.” There are a lot of steps between the theoretical concept of restoring an entire island and the reality; even with all that effort there were no guarantees. It did come off—spectacularly! Even as the vessel slows down to dock alongside the island’s only jetty, we are greeted by sounds almost lost forever: the haunting tapestry of strange and unexpected noises that demonstrate in the most exuberant way possible the reinstatement of a New Zealand bird community.
A sign—“Tiritiri Matangi Open Sanctuary”—greets
us as we step off the ferry, an explicit proclamation of the island as a place where visitors are welcome (although limited to a maximum of 150 per day); most of New Zealand’s other conservation islands have extremely restricted access. Before we move away from the jetty, a Department of Conservation officer welcomes us and explains a little of the history of the island, the extraordinary efforts that have gone into its restoration, and the critical responsibilities associated with keeping the continuing threats at bay. Undoubtedly, the biggest concern remains that of ensuring that mammalian predators do not reestablish. Remarkably, even though the island is only a few kilometers from the mainland, the only invasive mammal present before restoration was the Kiore, which was finally eradicated in 1994. But rodent invasion remains an ever-present threat; before the ferry left the Auckland terminal each passenger was required to check their baggage for rodents. It seemed a little extreme, but it was an appropriate indication of the seriousness with which the island’s stewards take their responsibilities. The challenge of keeping Tiritiri predator free is formidable, being such a short distance from a major city full of the usual vermin. So far, so good.
I had hoped that I might catch at least a glimpse of some of the species I had previously seen only in captivity but was not expecting this to be so effortless. As the track leads away from the beach into the dense restored forest, I am astonished to see plenty of Red-crowned Kākāriki (parakeets), Kererū (the large endemic pigeon), Kōkako (a strange crow-like endemic) and Tīeke (also known as Saddleback, another odd endemic) foraging in the foliage just above me, the birds apparently oblivious to the presence of overexcited humans. Their legendary lack of fear was a fatal flaw of many New Zealand birds, but it certainly makes the birding easy. It is also immediately obvious that these are not simply wild birds in the bush; almost all wear colored leg bands, direct evidence that, as well as being a sanctuary, Tiritiri is a functioning science laboratory. “Most of the translocated species are being intensively researched,” says Josie, who has been involved in many ecological studies here. “This entire exercise is an ongoing experiment, and we need to learn as much as we possibly can. For example, the first of these birds were brought to Tiritiri from other parts of the country. But would they find the resources they needed to survive and breed? What would they eat?”
Further along the track we begin to head downhill into a steep valley where the forest is particularly dense and dark, the entire area overshad-owed by the huge spreading canopy of several enormous and obviously ancient trees. “These are Pōhutukawa, the oldest trees on the island,” explains Josie. “Some of the very few to have survived all the clearing. They must be hundreds of years old.” The path is carpeted in their rich red flowers, a rare element of color amid all the dark greens. As we pause to admire these venerable trees, I am a little surprised to detect that telltale flitting behavior of birds visiting a feeder. Sure enough, just ahead is a box-like platform with a peaked roof supported on a pole. About a dozen or so small birds are dashing in and out, landing on the roof or entering the mesh box through a series of small holes. I recognize Tui and bellbirds, both fairly common honeyeaters found throughout New Zealand, but what I am particularly excited to see are Hihi (also known as Stitchbird), another a nectar-feeding species and one of direct relevance to this trip. Although drab from a distance, up close the main fawn-mousy brown plumage of the male is offset by striking yellow, black, and white. This is another of the really odd New Zealand birds, an ancient endemic species recently placed into a taxonomic family all by itself. The Hihi has also become famous among behavioral ecologists because of its highly non-traditional practice of copulating face-to-face, something unique among birds.21 But whatever their preferred sexual position, it has become clear that the really essential ingredient for successful reproduction in Hihi is sufficient sweet stuff: the rich carbohydrates normally supplied in the nectar and fruit these birds crave. These treats are abundant in the places where Hihi have survived but appear to be severely limited elsewhere. Including Tiritiri Matangi.
Helping Hungry Hihi
Along with so many other New Zealand birds, Hihi were almost entirely obliterated by the gray tide of introduced mammalian predators.22 As early as the 1880s, Hihi had been exterminated from the mainland, with the entire population limited to those present on the mammal-free Little Barrier Island.23 This thickly vegetated and mountainous island of 3000 hectares (7400 acres) located to the north of Tiritiri harbors numerous species that had either been exterminated or greatly reduced elsewhere and is therefore an extremely important sanctuary for many of New Zealand’s belea-guered birds. But Little Barrier is also just one small island, and because it carries the fate of so many vulnerable species, the risks of something going wrong are always high. A major storm, a wildfire, a virulent disease—or the arrival of rats or stoats—could have unthinkable consequences. To reduce this risk of extinction as well as contribute to ensuring the survival of many species, Little Barrier has served as both a continuing safe haven as well as a source of birds for translocation. In 1995, for example, the first group of Hihi was brought the short distance (about 50 km, or 30 miles) from Little Barrier Island to Tiritiri Matangi.24 By then Tiritiri had been thoroughly and carefully revegetated; it was quietly assumed that these birds would find their new home to their liking. After all, several other species had also been brought over to Tiritiri and were thriving.
The Hihi, it was discovered, are somewhat choosy when it comes to nest locations, preferring natural hollows, which were simply much rarer in the relatively young forests of Tiritiri. This was easily solved with the provision of lots of nest boxes; the birds took to these quickly and eggs soon appeared.25 Less straightforward was their sugary diet. While Tiritiri did have plenty of the nectar-bearing plants that Hihi like, the abundance of flowers and perhaps the quality of their carbohydrates seemed to be of a lower quality than those back on Little Barrier.26 What was much more obvious, however, was the level of vigorous competition over these sugar supplies. The presence of the much larger and more assertive Tui, as well as the sheer number of other “honey-eating” birds such as bellbirds, suggested that the Hihi were losing the competition for the limited supplies of sweet food.27 And without sufficient suitable foods, breeding was almost always unsuccessful, if it occurred at all. With the survival of Hihi being increasingly reliant on translocation to islands such as Tiritiri Matangi, this was an issue of direct and desperate importance.
Provision of supplementary foods was called for, although the type of food and the timing were not clear. Various concoctions and feeding regimes had been trialed at different locations, but careful monitoring of the birds found little evidence of success. A crucial breakthrough came with the conclusion of a 6-year experimental study of Hihi translocated to another island, Mokoia, which is located within Lake Rotorua in the famous geo-thermal region of the North Island of New Zealand.28 In research lead by Isabel Castro from Massey University, several different high carbohydrate supplements (supplied in modified hummingbird feeders) were positioned near the nest boxes of randomly selected breeding females, intentionally favoring the nesting bird by easy access to the goodies. “Unfed” females had to fly over 100 meters (110 yards) to visit a feeder and were unlikely to find any food left over. During the study, treatments were switched and feeders moved so that reliable comparisons could be made. In particular, the researchers were interested in assessing whether providing supplementary foods throughout the entire breeding season was important, previous experiments having been limited to only 2 weeks of feeding.
The first thing that the researchers noted was that the birds really did use the feeders a lot, and did so while incubating eggs and brooding chicks. Although they had to travel far greater distances, even the females without feeders nearby also visited feeders if they were able to. There was no doubt that the additional foods were being sought after. But the critical question was whether this made a difference in their reproduction. Having reviewed supplementary
feeding experiments in Chapter 5, we would probably expect some effect, but what Isabel Castro and her colleagues found was almost entirely unexpected—though very welcome. Females with access to the supplementary foods actually produced more eggs than those that did not, and more than doubled the number of young successfully fledged.29 For Hihi, the additional food was not simply useful; it was the difference between survival and death or extinction. This stark conclusion was re-inforced by the treatments without supplementary provisions: these birds simply were unable to breed successfully. These were remarkable findings— very few feeding experiments have altered clutch size—and of immediate relevance to those concerned with Hihi conservation. Given that almost all the locations being considered for translocation are recently restored islands (including fenced reserves on the mainland) with similarly limited food supplies, providing supplements more or less continuously seems to be essential for Hihi for the foreseeable future. Hence the feeders on Tiritiri and all the other places where Hihi have been reintroduced. For this special species, survival requires continuous intervention.