Minding the dotterels

Forest and Bird, Issue 266, 1 November 1992, Page 12

Minding the dotterels

Mark Bellingham

OTTEREL breeding areas are very vulnerable to human disturbance but they are also relatively easy to protect. The first breeding area to be protected with a fence and a warden was in 1985 at Opoutere on the Coromandel Peninsula (see Forest & Bird August 1989). The protection was financed by the Waikato branch of Forest and Bird. Protection schemes have also been successful at Waipu Spit and Ruakaka, and Forest and Bird field officers Ann and Basil Graeme and Fiona Edwards have taken the protection methods to additional beaches such as Ohope, Maketu and Omaha sandspits often

getting local schools and members of the community involved. Protection can be organised in different ways: by demarcating nesting areas with string or wire, posting educational signs, marking access paths or providing a warden to keep people and vehicles away. The area from which people are excluded need not be extensive nor the period prolonged. The birds do not require the whole beach to themselves and the colonies need be protected only during the breeding season. The schemes also help to educate visitors about the dotterels.

land and property. Vast areas of sand dune country, for example Ninety Mile Beach, have been planted in pine forest. As development reduces the availability of breeding habitat, the dotterel is being squeezed out. In what nesting habitat remains, breeding dotterels are at risk of human disturbance. Human disturbance is thought to affect shorebird breeding in two ways. Eggs and chicks may be directly destroyed (for example crushed by off-road vehicles) or disturbance can impinge indirectly by interrupting incubation or feeding of chicks. Typically, an incubating or brooding dotterel responds to a perceived threat by leaving the nest or chicks and trying to distract the intruder when it is still some distance away. The impact of directly crushing a nest or chick is obvious, but the effects of interrupting normal parenting may be just as serious. Repeated absence from

eggs or chicks due to frequent or sustained disturbance may result in their chilling or overheating (depending on weather conditions). The number of people on beaches is probably greater on sunny days when eggs may overheat in as little as 20 minutes. When the birds are forced to make frequent trips to and from the nest there are also more opportunities for scavenging birds or other predators to detect footprints or abnormal movements, and prey on unattended eggs. Black-backed gulls, which have

increased in numbers with the increase in food supplies from landfills, meatworks and fishing operations, are known to take dotterel eggs or chicks. During the 1989-90 season comparisons of New Zealand dotterel breeding success were made between ten beaches subject to low levels of human disturbance and ten subject to high disturbance. Dotterels at high disturbance beaches fledged, on average, only half as many chicks per pair (0.31) as did dotterels at low disturbance sites (0.62). UT THERE IS good news. Breeding dotterels are relatively easy to protect from human disturbance by simply keeping people out of nest-

ing areas (see panel). Habitat protection, however, is more difficult because it requires us to conserve some beaches in their natural state rather than developing them. Important New Zealand dotterel sites were identified in the October 1989 and February 1990 population censuses coordinated by the Department of Conservation. The conservation emphasis at these sites must be on protecting habitat before it becomes degraded. Pristine dune systems are now very rare. Those remaining should be protected from development by law. A public education campaign is required. DoC’s forthcoming recovery plan for the New Zealand dotterel should include liaison with regional councils (which administer coastal areas), local councils, schools, environmental groups, community groups and the general public. Local communities, which have made tremendous efforts to clean up litter in "Adopt a Beach" campaigns, must be encouraged to expand their efforts to also take responsibility for their local wildlife. The New Zealand dotterel is unique to New Zealand. Let us be determined to see this delightful bird continue to grace our beaches, now and into the future. % Andrew Cumming is a policy analyst at Waitakere City Council, Associate Professor Peter Jenkins is recently retired from the Zoology Department of the University of Auckland and John Hay is Director of Environmental Science at the University of Auckland. Their study was supported by grants from the New Zealand Lottery Grants Board and the Omithological Society of New Zealand.

N LATE 1988, my wife Elaine Murphy and I began a comprehensive survey of the Stewart Island birds. We systematically searched the open mountain tops for breeding sites, checking one or two new areas each season. We also began banding chicks and adults; from our band sightings and aided by a few previous records, we found that after each breeding season the birds gather in three flocks. One of these is not on Stewart Island but at Awarua Bay, near Bluff. Band sightings there confirmed what had been suspected for some years — that the Awarua Bay flock actually consists of Stewart Island birds that cross Foveaux Strait to winter on the mainland. Our banding also revealed that the largest flock, based around feeding grounds in Paterson Inlet, was highly mobile. Each day the birds fly across to Mason Bay on Stewart Island’s west coast and roost in the sand dunes there, but at night they cross to the east coast and roost at The Neck. They are therefore commuting from one side of the island to the other and back, a round trip of some 60 km, every 24 hours. The third flock feeds and roosts on the remote tidal flats at the head of Cooks Arm, a shallow reach extending west from Port Pegasus at the southern end of the island.

By adding the numbers of birds in _ these three flocks each autumn and allowing for a few juveniles wandering elsewhere, we can now make an accurate annual estimate of total numbers. In 1990, the whole southern population was about 100-105 birds, a marked decline since Ross McKenzie’s count 35 years earlier. The more we looked, the worse the situation became. We had hoped that the population might have stabilised at about 100, but in 1991 it was down to 80. Trying to be optimistic, we suggested that it might just have been an unusually bad Zs2g> .

season, but 1991-92 was just the same. This year there are only 60-65 birds; some of these are juveniles and some of the surviving adults may not have mates. There are probably, in fact, only about 20 breeding pairs left. What is causing such a rapid decline? A lot of the problems faced by New Zealand dotterels breeding in the North Island simply don’t exist on Stewart Island. Like most of the birds once found in the South Island, Stewart Island dotterels breed inland on exposed mountain tops, where there is virtually no disturbance by people, dogs, stock or vehicles. There is also plenty of suitable habitat available. However, our banding studies show that considerable numbers of adult birds are disappearing each season; this and other

evidence suggests that predation is the main problem. As there are no ferrets, stoats or weasels on Stewart Island, we think feral cats are the main predator, probably taking adult birds on the nest, although ship rats could be a problem too. Why this is happening now is something of a mystery. Cats and rats have probably been present on Stewart Island for 150 years or more — if they had been killing dotterels at the present rate for long, the population should have disappeared many years ago. Has the density, distribution or diet of

cats on the island changed in the past 40 years? We simply don’t know. Whatever the exact reasons for the decline, it can’t go on much longer. One of the main problems in trying to manage these birds is that their breeding grounds are widely scattered, in difficult terrain and there are few birds at each location. Protecting more than a few pairs is now feasible only at one site — around Table Hill, at the northern end of the Tin Range. Our findings suggest that if nothing is done to help the Table Hill birds within the next two seasons, the whole population will be past the point of no return — it will simply be too difficult and expensive after that to protect enough birds to ensure that the population survives.

HAT WOULD WE LOSE if the New Zealand dotterels on Stewart Island died out? While the genetic work that would decide whether the Stewart Island birds are a separate sub-species has not been done, our study has shown that there are considerable differences between northern and southern birds. Most biologists and conservation managers agree that we should make every attempt to preserve such diversity, whether the differences are due to genetic or behavioural variation. There is another important considera-

tion — if we lose the southern population there will be a drastic reduction in the overall range of the species. A few New Zealand dotterels are seen wandering the South Island coast each year and some of these birds even reach Farewell Spit. Our banding studies suggest that these are juveniles from Stewart Island. If that population is allowed to die out, there will probably be no New Zealand dotterels south of Cook Strait. What can we do? The draft recovery plan for the New Zealand dotterel suggests that the highest priority for work on the species should be to try and reverse the decline of the Stewart Island population. Our only practical option seems to be to control feral cats around Table Hill, the last remaining major breeding site. We know that some juveniles are still produced each season, suggesting that if we can reduce the adult mortality, the population will be able to recover. With this in mind we put forward a proposal to ring the area with poison bait stations to try and keep cat numbers in the vicinity as low as possible during the breeding season. This involved the use of a new long-life bait, developed specifically for DoC by the Forest Research Institute. In September came the welcome news that DoC had decided that the cat-con-trol programme should go ahead this season. We will be monitoring its effec-

tiveness closely and, at the same time, taking small blood samples from a few birds so that genetic tests can be made. These will allow us to check for differences between the Stewart Island and North Island populations. Earlier this year, a memo on management priorities emerged from the Protected Species Policy Division of DoC, recommending that certain listed species "are candidates for reduced level of activity". In effect, this suggested that DoC conservancies around the country spend less time and money on them. The New Zealand dotterel is on that list. Presumably because the department is short of money, the whole species is now designated as one of conservation’s secondclass citizens. Already, DoC has stopped the direct funding for the full-time warden at Opoutere this coming season (see page 12) as a direct result of this reduced status. To those of us involved in trying to help the New Zealand dotterel, this is a particularly ill-timed blow. Just as the species is starting to get some of the belated public attention it deserves, just as the draft recovery plan is completed, the rug is pulled from under our feet. In spite of the critical situation on Stewart Island, the Protected Species list makes no dis-

tinction between northern and southern populations, although the approval for the cat-control programme suggests that the priority of the southern birds may now be under review. The New Zealand dotterel may be endemic, threatened and declining. It may be down to less than 1,500 individuals, with one of its two populations critically endangered, but all this is no longer enough — there are too many species in the same boat. DoC simply does not have the financial resources to act. Currently, New Zealand prides itself on being a world leader in threatened-species conservation, but its hard-earned reputation in this field will not last long under these conditions. This lack of money means that the dotterel, like other species, will probably have to rely heavily in the longer term on sponsorship, volunteers and public involvement for its conservation. How can we raise the New Zealand dotterel’s public profile? It’s not easy. In most people’s eyes, a small brown shorebird simply can’t compete with media stars like the yelloweyed penguin, in spite of the fact that there are nearly five times as many of the penguins. Those who know the New Zealand dotterel find it a fascinating, attractive and

endearing animal. The sad fact is that like much of our endemic fauna it is illadapted to cope with today’s problems — the predators, disturbance and habitat destruction; this is hardly its own fault of course, but it does need our help to survive. I believe it would be reprehensible and tragic if these distinctive Stewart Island birds were allowed to become extinct without a determined effort being made to save them. Acknowledgements Sincere thanks to DoC staff (past and present) on Stewart Island for a great deal of support, and to Maida Barlow for data from Southland. Thanks also to DoC (Science and Research Division), the New Zealand Lottery Grants Board and the Ornithological Society of New Zealand, who all provided funding for various parts of the Stewart Island study. +

Dr John Dowding is a research biologist based in Christchurch. His main interests are in our endemic birds and their predators. He has been studying New

Zealand dotterels in the North Island for six years and recently wrote the draft species recovery plan for DoC.