The curse of the lorikeet

Forest and Bird, Issue 292, 1 May 1999, Page 24

The curse of the

lorikeet

By

GORDON ELL

our countryside.

Cage birds released into the wild are only one of the ways ‘Australian birds’ take over

Te strong, beautiful, breeding and dangerous. The rainbow lorikeet is yet another example of how foreign bird species are changing New Zealand’s ecology, threatening our native birds. The Australian lorikeet has feeding habits which place it in direct competition with our native species, as the birds form growing flocks and raid flowering trees and fruit, particularly on the North Shore of Auckland. They also compete with some native species for scarce nesting habitats. Yet the illegal release of rainbow lorikeets in the suburbs of Auckland has been supported by a small body of people who see them as a ‘valuable addition’ to our range of urban birds. Unfortunately, official action to eradicate this obviously dangerous bird has been slow in coming. Meanwhile lorikeet numbers multiply and the risk of their invading neighbouring bird refuges in the Hauraki Gulf escalates. The man accused of releasing the lorikeets appears quite unrepentant, defending their place in the wild, and soliciting public support for them. He was also reported by the North Shore Times Advertiser as offering $10,000 to the Department of Conservation to help save kakapo if it would drop plans to capture the lorikeets. The rainbow lorikeet has already spread beyond the North Shore, where flocks approach 50 birds, with more reported across the harbour as far away as Mt Albert, Remuera and Glendowie, and possible sightings further south. Thanks to campaigning by Forest and Bird activists, the Department of

Conservation has taken some initial action with the Auckland Regional Council to capture the lorikeets. Anecdotal evidence against the lorikeets on the North Shore includes their rapid breeding and spread, their natural aggression towards native species, and their competition with native tui for nectar. If the birds reached nearby nature sanctuaries, such as Tiritiri Matangi Island just offshore, they would immediately threaten the nectar sources of bellbird and stitchbird too. Lorikeets are also fruit eaters thus competing with birds reliant on that food source. The New Zealand Fruitgrowers’ Federation has joined in pleas to have the birds declared a pest — its concern is based on the impact of the species on Australian fruitgrowing, particularly in Western Australia where the birds have been introduced. As hole nesters, lorikeets would also compete for nesting habitat with native red-

crowned parakeet, saddleback and other species. Nest holes are difficult to find in most forests, as old-growth trees are lost, and possums, starlings and mynas compete for holes. (On Tiritiri Matangi, which has a comparatively young forest, nest boxes are already needed to sustain the population of hole-nesting native birds). A co-operative venture between the Ministry of Agriculture and Forestry, the Auckland Regional Council and _ the Department of Conservation originally aimed to capture the birds, offering some to the zoo. Others would be tested for the range of diseases that lorikeets carry in Australia, including some which may affect native parakeets, and others of public health concern, including salmonella, avian cholera and avian tuberculosis. The rest would be destroyed. An initial attempt during February resulted in 27 birds being captured, at which time the cage-bird enthusiasts argued the birds should be put back in cages (they're worth from $200-$265 each) rather than put down. Since then work has stopped, for a couple of months at least, while the Department of Conservation prepares a ‘capture plan’ for the rest of the birds. It seems there are also some legal ambiguities to be worked through, a clear signal that the laws about capturing unwanted birds need an overhaul.

uckland, and the north generally, as: several species of wild birds which usually don’t occur elsewhere — bred from birds which have ‘escaped’ from cages into a warmly welcoming environment. The suburbs already contain a small but widespread population of Malay spotted doves and some ring-necked Barbary doves. The shriek of sulphur-crested cockatoo gives a harsh Australian accent to the kauri forest of Centennial Park, Waitakere. An escaped population of Australian galahs is recently reported to have spread from Ponui Island in the inner gulf and into last regional haunt of the kokako on the mainland, in the Hunua Ranges on the southern edge of Auckland. The eastern rosella of Australia is already widespread, from North Cape through to the eastern Bay of Plenty and Waikato, extending into Taranaki. These birds occur in the vicinity of other New Zealand cities too, particularly in Wellington and Hutt Valley, with wild populations of these former cage birds spreading into the Wairarapa, Hawkes Bay, Horowhenua and Manawatu. There is also a core population about Dunedin. Wellington also has a population of the closely related crimson rosella, another popular cage bird. Rosellas are often mistaken for native parakeets, which have similar feeding patterns but are now restricted to the remote corners of our forests. Another valuable cage bird, the sulphurcrested cockatoo has established several wild populations, particularly in Wellington, in the Turakina Valley of Rangitikei, and the coastal hills of Waikato. Many blame cage escapes for these populations, though it is likely some colonies formed after legal introductions in the early 1900s. These large white parrots may occupy much the same breeding and feeding niche as our own kaka and therefore their place as wild birds in New Zealand needs to be carefully watched. Fortunately, their shop value of around $1250 has been a factor in slowing their spread as people catch them for sale.

etting rid of an unwanted population of exotic birds has been done before. In 1952, a number of red-vented bulbul, a popular cage bird from India and south-east Asia, were apparently released from a ship entering Auckland Harbour. Mindful of their impact elsewhere in the Pacific region (the birds may be seen in suburban Sydney and Fiji, for example) the Department of Agriculture determined to exterminate them. It took till mid-1955, to find and kill 52 birds between Takapuna and Mount Eden in central Auckland. This timetable can be set against the lack of progress in eradicating wild populations of the rainbow lorikeet, of which a greater number have already spread through a larger area. The problem of ‘avian pests’ — birds which take the place of native species — is a controversial one. Sometimes, as with the rainbow lorikeet, the issues are clear and something can still be done to stop the birds. In other cases, for example the Australian magpies and the Indian myna, the immigrant birds are already so widespread that ‘control’ is more likely than eradication. Many people are attracted by the lively calls of these introduced birds, and by their anthropomorphic behaviour. The late Jacqui

Barrington, however, drew attention to the destructive habits of magpies (and mynas), particularly in the Forest & Bird journal for August 1996. Their aggressive behaviour towards other birds has been further documented recently by Department of Conservation rangers who have described how two magpies singled out a kaka at Makarora near Wanaka, drove it to the ground, and killed it. Only with frequent reminders that magpies kill other birds will popular attitudes change and their pest status be widely recognised. acclimatization, the natural migration of foreign birds is also a significant dynamic in their population of New Zealand. The past 50 years have seen the spread of several waves of successful bird immigrants from Australia. In that time white-fronted heron, welcome swallow, Australian coot and spur-winged plover have all spread through the country to become common birds. Their impact has not been fully measured, though there is anecdotal evidence that the highly efficient welcome swallow, outperforms the fantail in its hunt for insects, which may have suppressed local populations of the native bird. The aggressive territorial nature of spur-winged plover is also said to affect other species, though these arguments are contested. While circumstantial evidence against them grows, so does the population which has spread widely in the South Island, and through the North Island during the past decade. Questions which might have settled the matter scientifically don’t seem to have been asked in time to make an informed choice. As self-introduced birds they are automatically protected. Scientists describe New Zealand as having a ‘depauperate avifauna’ — that is the countryside has comparatively few species with consequent habitat ‘gaps’ which some new species may readily fill. Further, not only have many of our original birds been radically reduced in number but the habitats they once enjoyed have also changed. Maori settlers burnt up to a third of the forest, for hunting, for gardening, and to encourage the growth of bracken fern, the root of which was a staple food. European settlers followed, burning and clearing a further third for farmland. New Zealand of the year 2000 has only 10 percent of the wetlands it had when the Treaty of Waitangi was signed in 1840; river systems, lakes and coastal habitats have also been extensively modified by development. As a result of this, and the introductions of mammalian pests, three-quarters of our native bird species are now classed as ‘threatened. At the same time, it has : eaving aside unofficial and official

become easier for some kinds of new immigrants to find a suitable habitat with the expansion of grassland farming. The foreign bird ‘invasion, however, has gone on for a very much longer time than this. Fossil remains indicate some Australasian birds have been here thousands of years; others a million or more. The self-introduction of the familiar white-eye, waxeye or silvereye, however, occurred as recently as 1832, with the birds becoming widespread during 1856. Their comparatively recent arrival is recorded in their Maori name of tauhou or ‘stranger’. A closer look at the pedigree of many of New Zealand’s native birds reveals them to be the same species, or at least a closely related sub-species, to those also found in Australia

or even the Indo-Pacific region. Examples include the Australasian harrier, the morepork (Australian boobook owl), the pied fantail (Australian grey fantail), the banded rail of the western Pacific and IndonesiaPhilippines, pied stilt, and the pukeko (the cosmopolitan purple gallinule). Many of our gulls, terns and shags occur elsewhere. Some of these self-introduced birds have been here a very long time — the takahe is believed to be a local flightless descendant evolved over millions of years from the ancestral purple gallinule — while the selfintroduction of the pukeko and the New Zealand subspecies of the sacred kingfisher may date back only a few hundred years. Making a value judgement between such historic self-introductions, now our ‘native birds, and those new species which are still arriving is generally too difficult; the law simply finds that a new self-intro-duction, a natural arrival, should be classed and protected as if it were a native bird. Thus the nankeen night heron from Australia, which bred for the first time by the upper Wanganui river in 1994, is protected as much as the endemic takahe. The wisdom of automatically accepting such self-introductions could be questioned. For example, there is plenty of anecdotal evi-

dence that spur-winged plover attack other birds but some scientists say this is not conclusive enough. Self-introductions of potential insect pests are not so casually accepted. It could be argued the time has come to review the ‘automatic protection’ of birds and assess the likely consequences of selfintroductions on other species before extending them full protection as a ‘native’. or ‘exotic’ species, which appear to have no deleterious effect on the environment (or other birds), protection might seem an adequate reward. Yet any formal attempt to introduce a new species of bird would surely lead to a round of environmental impact assessments. There would

doubtless be fulsome objection from those who feared a new bird might affect the viability of populations of rare and endangered ‘native’ birds. Forest and Bird, for example, is adamant that new introductions are totally inappropriate, unnecessary, and a further threat to our native species. Fortunately, the release of cage birds is already illegal but the case of the lorikeets shows such laws may need more rigorous enforcement. The ambiguity of ancestry among our native birds makes it rather difficult to rank the relative importance of our species, particularly in terms of world rarity. Obviously the endemic birds — those occurring in New Zealand alone — are of special concern. These are the ones often at most risk, if not already extinct. The ancestors of birds like the flightless moa, the adzebill and the kiwi, evolved at a time when New Zealand was still part of the ancient supercontinent of Gondwana. In a New Zealand isolated by ocean, they filled the niches occupied elswhere by mammals which had not evolved when New Zealand became separated from today’s southern continents. When Maori, with dog and rat, settled New Zealand perhaps 1000 years ago, the ecology began to change. When moa were hunted to extinction, the giant eagle which fed on them

also vanished. Around 32 species of bird, including various moa and rails, the native goose, a pelican, ducks and swan, were lost during Maori times, unable to sustain harvest or competition from the new mammals. Since European settlement another 11 species have vanished while more have been driven to the brink of extinction. Loss of habitat has had a major influence on bird numbers, but so has the introduction of new species of mammalian pests and birds which have changed our natural environment, forever. On the open country European finches, sparrows, starlings and mynas have replaced the New Zealand quail, weka and other scrub species. On the wetlands, introduced mallard ducks are rapidly taking the place of native grey duck, with which they interbreed. In the lowland forests of New Zealand, European blackbirds rake about the leaf mould for food, in many places more common as a species than the native robin. In higher forest the piping sounds of introduced chaffinch and redpoll are usually more distinct than the chattering of native whitehead, or yellowhead (mohua) and brown creeper. The introduced common and garden birds of New Zealand may all seem a ‘threat’ to our native species, but obviously the days of putting this to rights is long gone. Many of the peculiar endemic birds have already been lost. The test that needs to be applied to the many immigrant species already flourishing here is whether their acclimatization should be tolerated further, if they are affecting our remaining native and endemic birds. With escaped cage birds the choice is a clear and easy ‘never’. Logically, with self-introduced species such the spur-winged plover (and the nankeen night heron), questions need to be asked about their likely environmental impact before they spread too far. Our native birds don’t need more competition; and most of them need more help. The author acknowledges the distribution records of the Ornithological Society as summarised in the Field Guide to the Birds of New Zealand by Barrie Heather and Hugh Robertson, (Viking, Auckland 1996).

Author GORDON ELL enjoys Australian birdlife when it is in Australia. A cage bird escapee in New Zealand, this crimson rosella was photographed in the wild at Bunya Mountain National Park, in southern Queensland.