Evidence of these changes can be seen on our own shores. The number of bar-tailed godwits or kuaka making the 17,000km migration from Australia and New Zealand to their breeding grounds in the Arctic each year has fallen dramatically as a result of habitat loss internationally.
Along the way, the birds stop to rest and gather food at the Yellow Sea mudflats in China, North Korea and South Korea. BirdLife International’s annual State of the World’s Birds report said this year that these mudflats have been progressively lost to land reclamation for agriculture, ports, industrial developments and urbanisation. Two-thirds of the Yellow Sea’s intertidal habitat has been reclaimed since the 1950s. In China, nearly 40% has been lost since the 1980s. Shorebird populations in the area overall have declined an estimated 43-78% over the past 15 years.
In New Zealand, the impact of these changes is clear. The number of godwits migrating to Southland each year has halved from the 4000 that used to arrive each spring in the 1970s and 1980s. Over the past decade, the number of godwits visiting the Manawatū Estuary each year has fallen by about a third.
Of the 168 species of native birds in this country, only 20% are in good shape. One in every three, the then Parliamentary Commissioner for the Environment Jan Wright wrote in her 2017 report, “Taonga of an Island Nation”, “is not far off from following the moa and many others into extinction. The situation is desperate.”
Endemic birds, long adapted to the New Zealand environment before the arrival of humans and predators, are in most difficulty, Wright wrote. Three – pīwakawaka (fantail), tūī and the riroriro (grey warbler) – have increased their ranges over the past few decades. Of the rest, 13% are doing okay, but 45% are “in serious trouble”.
New Zealand is not experiencing the wholesale collapse of urban bird populations occurring in Europe and the US, but there is cause for concern. Recent results from the New Zealand Garden Bird Survey show that, since the survey was launched in 2007, six of even our most common garden bird species have fallen in number – goldfinch, chaffinch, dunnock and blackbird by 10-16% while starling and song thrush numbers have plummeted by almost a third. Tauhou (silvereye), our most common native garden bird, has almost halved over the same period. As the report says, it is tempting to dismiss changes to introduced species, but “they are signalling changes in our urban and rural environments that we need to better understand”.
Some of our native birds have fared better.
Tūī have increased by an average 22% across the country, in particular in Hamilton and Blenheim where restoration programmes are under way.
Kererū have increased by 12% and pīwakawaka by 8. But Yolanda van Heezik, an urban ecologist at the University of Otago, cautions that we are heading down a similar path to Europe’s.
“In other countries you see a slow loss of green space in people’s gardens as they pave over areas for driveways, patios or buildings – all the time you are losing land.”
Some new housing developments include bird-pulling landscaping – small areas of marshy wetland, called swales, and riparian plantings near watercourses. But van Heezik describes others as “just dire”. House plots are getting smaller – the average section size has fallen from 1012sq m to about 450 since the 1970s – and the houses themselves are getting bigger – in the past decade, the average size of a new dwelling has jumped from 107sq m to just under 175 – in 2012, it topped 200.
In her report, Wright identifies the need to increase the genetic diversity of threatened species. Restoring populations of endangered bird species on islands and within fenced sanctuaries protects them from predators, but it also reduces genetic diversity, leaving small populations vulnerable to the impact of disease and habitat degradation. Despite the laudable efforts put into kākāpō and kōkako, for example, isolated bird populations can become inbred and struggle to produce healthy chicks. Bandit, a kōkako on the Tiritiri Matangi island sanctuary in the Hauraki Gulf, she writes, is consorting with his grandmother: “This may be a happy relationship, but it is unlikely to be a healthy one. We must guard against our birds drifting to the shallow end of the gene pool.”
Such findings point to the importance of restoring and protecting a resilient and diverse bird population on the mainland, not just on “bird ‘museums’ on offshore islands that few can ever visit”.
Restoration of bird populations has traditionally focused on land under Department of Conservation administration, but urban ecologists are increasingly looking to cities to fill that gap. In Dunedin, 36% of the city is covered by gardens, “so if you can improve the diversity in those gardens,” says van Heezik, “you are making a significant contribution towards providing resources for a lot of species. I have been pushing the role of gardens as ways to provide habitat in themselves and to connect parks and reserves where there are good resources.”
The shrinking garden
Gardens are shrinking or being confined to pots and narrow borders and changes to the Resource Management Act have made it easier to cut down the large trees used by tūī, moreporks, kingfishers and blackbirds to proclaim their territory, and by kererū as a launching pad for their aerial displays.
The result is that the land for bird habitat land is being lost. On average, 2% of our inner city areas are covered with native vegetation (on the urban-rural boundary, it’s more than 10%). But, says Bruce Clarkson, ecological restoration expert at the University of Waikato, once the total cover of a district falls below 10%, “you lose a disproportionate number of species”.
New Plymouth, with its native bush and gully topography, is the only city close to the ideal 10% for inner-city indigenous vegetation; in Wellington or Nelson, where the surrounding hills are too steep for development, the cover density is higher than in Napier and Hastings, which have more gentle terrain.
Although urban cats are estimated to be responsible for between five million and 11 million bird deaths a year, cities have advantages for birdlife: there are no grazing animals to disturb nests or decimate young seedlings, and fewer mustelids (weasels, stoats and ferrets); it is easier to monitor numbers and there is a willing workforce of homeowners and volunteers to trap pests, control weeds and replant native flora.
“This is the new frontier for conservation in New Zealand,” says Clarkson, leader of the People, Cities and Nature research programme, which is aimed at restoring urban indigenous biodiversity. “We have done all the work on offshore islands, and now we have moved into the mainland islands. The last remaining part of our landscape where we haven’t quite worked it out is the urban environment.
“If we can get people to recognise the biodiversity in their backyard, they are more likely to support wider efforts on a regional and national scale. That would be the way to reverse the decline across the region and the nation. We have done a reasonable job (in the back country) but people are disconnected from it – how many people get a chance to visit Stewart Island?
“To solve biodiversity decline, we need a fully engaged public who understand the importance of nature, and the best place for people to experience it is where they live.”
In Clarkson’s home town of Hamilton, locals are throwing their weight behind ecological restoration projects in the city’s gullies and at Waiwhakareke (Horseshoe Lake) in a natural heritage park on the city’s northwestern fringe. The resulting increase in native bird populations, he says, is clear proof of the value of such efforts.
“In my first 15 years in Hamilton, I saw tūī twice, and then only for very brief visits. Now I hear them every day – they are fully recolonised and nesting within the city. They are all over the place. So yes, we need the offshore island reserves, we need the mainland island reserves but we also need to work in urban settings.
“New Zealand is one big ecosystem, and whatever you do in one part of the system affects the others. We have to have an integrated approach where we are looking after offshore islands, where we have mainland islands and where we are looking after the urban environment because birds and plants operate on the regional and landscape scale. They don’t just work in little bits here and there.”
Across the country, the main threat to our native birds is predators: possums, rats, stoats, ferrets, weasels, cats and hedgehogs kill millions of birds every year and feed on insects that sustain our bird population. Stoats have played a role in the decline of threatened species such as the rock wren, black stilt, kākāpō, and kōkako. They also eat up to 60% of young kiwi. Possums kill sooty shearwater (tītī or muttonbird), the brown kiwi, North Island kōkako, saddleback, pīwakawaka and Westland black petrel (tāiko).
The millions of feral cats that populate our countryside and forest margins decimate the wading birds that live in the braided riverbeds of the South Island.
Rats have contributed to the decline of the South Island saddleback, the Stewart Island snipe, the North Island kōkako, kererū, kākāriki and mōhua (yellowhead). Exotic social wasp species compete with tūī and korimako (bellbirds) for honeydew on beech trees, and invasive plants, such as old man’s beard, banana passionfruit, wandering willy, Japanese honeysuckle, climbing asparagus and lupins, swamp and choke native flora and provide perfect cover for feral cats and ferrets.
New Zealand is home to some 2264 introduced species – 30 mammals, 34 birds and 2200 plants – competing with, or predating upon, indigenous species. Most of the line-up in this rogues’ gallery came at our invitation (stoats were introduced to curb the out-of-control rabbit population but they largely ignored the rabbits and zeroed in on native birds), we have not ignored the problem.
Since Te Anau bush guide Richard Henry took on the job in the 1890s of transferring over 700 kiwi and kākāpō to Resolution Island off the Fiordland coast, there have been many initiatives to address these threats. The area of public conservation land has increased from 7,000,000ha in 1990 to 8,500,000ha; about a third of New Zealand lies within the conservation estate. Some 170,000 ha of land are protected under QEII covenants; a further 171,700 ha are held under Ngā Whenua Rāhui 25-year convenants or kawenata.
Pest control is having an effect – in South Westland’s Landsborough Valley, native bird numbers have doubled, largely as a result of valley-wide trapping and aerial 1080 drops. Only two species, tautou and the migratory koekoeā (long-tailed cuckoo), have declined in number.
The Cacophony Project, developed by Christchurch inventor Grant Ryan, is trialling a device that will recognise predators in the bush and pepper them with a blast of 1080 pellets.
Research into new genetic techniques, including gene-drive technology that aims to drive infertility through a population of predators and predator-specific toxins, are under way.
However, aerial application of 1080 remains essential for the foreseeable future, until innovations in trapping and ground poisoning become more reliable.
With its systems of predator control and predator-free sanctuaries, Wellington has become a poster child for the restoration of urban bird populations. The council’s 2017 Bird Report shows the reintroduction of bird species that had been falling in numbers locally, including kaka, kākāriki, korimako and pōpokotea (whitehead), to predator-free sites such as Zealandia, Matiu/Somes Island and Mana Island has established healthy populations which have since spread into nearby forested reserves. Last year, the increase in kererū numbers prompted the Wellington City Council to install “Slow for kererū” road signs at key locations around Zealandia and Otari-Wilton’s Bush.
In Christchurch, far from the new subdivisions, the earthquake has thrown up an unprecedented opportunity to restore a wetlands habitat suitable for native bird populations. In the red zone along the Avon River, where whole suburbs have been demolished, overgrown gardens, abandoned parks and pathless riverbanks are already alive to the sound of blackbirds, thrushes, ducks, shags, even the muted call of the native scaup or papango. According to one neighbour, korimako (bellbirds), once a rare visitor to this area, are heard regularly.
The long-awaited proposal for this sinuous sliver of land, put together by crown-council joint enterprise Regenerate Christchurch, advocates a green spine, a 345ha river corridor extending 11km from city to sea, with areas for sport and recreation, community spaces and food and cultural opportunities. Tying these together is a strong focus on the restoration of the natural wetlands environment, providing natural systems of flood mitigation, improved water quality and a restored native habitat for fish and birds. Landcare Research ecologist Colin Meurk gives the plan a thumbs up “as far as it goes” but there are more opportunities, he says, that could have a lasting impact on the natural history of our region.
Meurk is leading the push for a fenced ecosanctuary encompassing the neighbouring 120ha Travis Wetland and linked to the red zone with a wildlife bridge, providing higher ground for times of floods and inevitable sea-level rise and a pest-free habitat for some of our most treasured bird species.
“We have some very unique species on the world stage, which we have a duty to look after and which help define our identity and sense of place. But extinction of experience leads to extinction of species. If people grow up not knowing something exists, if they have no personal connection with it, they have no desire to protect it. Canterbury is the only region in the country that doesn’t have a sanctuary for its citizens to engage with endangered wildlife species, but having opportunities where people can look face-to-face at a kākā or takahē or kākāpō is a vital part of creating that connection.”
Such sanctuaries, he says, inevitably have a “halo effect”, whereby small populations of birds, once established in a secure environment, will spread out across other wildlife parks in the city and out across the plains, so avoiding the risk of inbreeding.
The human factor
With mounting pressure on our bird populations, they need all the help they can get. Our human population is expected to hit five million by 2025 – current projections are for the Auckland region to reach two million by 2031 – and the demand for new housing is already putting pressure on bird habitats. Last year, the Government passed legislation revoking the reserve status of the Point England Reserve in east Auckland to sell almost 12ha, about a quarter of the reserve, to Ngāti Paoa to build 300 new houses – this despite widespread concern about the impact on roosting grounds for a number of shorebirds, including the New Zealand dotterel, the “nationally critical” shore plover, white-faced herons, royal spoonbill, pied stilts and various oystercatchers.
Two-thirds of our indigenous forest cover has disappeared since humans arrived on these islands. Rivers have been drained, streams buried, estuaries filled in – nearly 90% of our wetlands have been modified for land development or drained for agriculture. Connecting pathways have also been degraded and although some birds will fly between isolated remnants of habitat, others, such as the rifleman and saddleback, will not cross even short stretches of open land or water.
Pressures to clear land for human use have knock-on effects on our natural environment. In eating and dispersing seeds, birds maintain forest diversity – karaka trees, for example, are heavily dependent on kererū; the flowers of the rare pikirangi (mistletoe) are pollinated by honey-eaters such as tūī, korimako and hihi (stitchbirds).
And encounters with the natural environment, argues Clarkson, are essential for us. He cites US non-fiction writer and journalist Richard Louv, author of Last Child in the Woods. In this book, Louv warns against “nature deficit disorder” as the cause of childhood malaises such as obesity, attention disorders and depression.
“About 87% of us live in towns and cities and many have no connection with nature,” says Clarkson. “We have a generation of young people who are essentially disconnected from the environment. But humans have an innate requirement to connect with nature. If they don’t do that in a satisfactory way, they will become unhealthy, psychologically and physically. But if you get all the ingredients in place, just give native species half a chance and they will reassert themselves.”
This article was first published in the July 7, 2018 issue of the New Zealand Listener.