Waitere

Forest and Bird, Volume 15, Issue 4, 1 November 1984, Page 22

Waitere

By

DSIR journalist

Allan Bell,

Native shrubland in an exotic sea

Waitere is 1650 hectares of scrubland — still regenerating after decades of fires — which shelters probably the largest population of kiwis in an isolated remnant in the Hawke’s Bay area. It lies 20 kms inland towards the Mohaka River from Tutira on the Napier-Gisborne highway. The Waitere block is Crown land, and last year it was scheduled to be cleared for farmland. It is also the site which the Agricultural Ecology section of DSIR’s Ecology Division chose for a study on the effect of land clearance on kiwis. The research has been carried out from the section’s base in Havelock North by Dr John McLennan and two short-term workers, Murray Potter and Mark Robinson.

The original research plan was radically modified by the discovery of the relatively dense population of North Island brown kiwi (Apteryx australis) at Waitere. Residents thought that no kiwis lived there, but in the first two nights fieldworkers located five birds. When the Napier branch of the Royal Forest and Bird Protection Society heard of the kiwis’ presence in January 1984, they called for the block to be reserved. The Lands and Survey Department halted clearance, and in August released a management plan, which is open for public submissions until November 16. The management plan designates a third of the block to be cleared, with any resident kiwis being relocated. The

remaining 1000 hectares will be under a three-year moratorium while Lands and Survey evaluate plant and bird life more closely. This moratorium zone contains at least 24 known kiwis, including three chicks. The Department is to study the feasibility of shifting these kiwis also, and maintains the right to cut a road across the middle of the block. Scrubland studies The Waitere study is one part of a largescale project, under the leadership of Dr Mike Rudge, researching scrubland from the ranges to the coast. Thirty percent of New Zealand’s land area is covered in scrub. A lot of wild habitat such as gullies, shelterbelts and riverbeds remains scattered across the highly

Managed agricultural and horticultural land of Hawke’s Bay. Yet the amount of Scrub has been reduced by over half since the region was mapped 13 years ago. Work by another member of the research team, Bruce MacMillan, involved a year of monthly five-minute bird counts at 21 sites across Hawke’s Bay. He has shown that scrub is a valuable habitat for native birds, sometimes with a richer birdlife than native forest. Some birds largely live in the scrub, such as bellbirds which proved to be much more common in scrub than bush.

Of particular value are the uncleared river valleys, which may serve as corridors by which birds migrate between the back country and the coastal plain. The research has also shown that, as well as being a possibly unique regional kiwi habitat, Waitere scrub is valuable for a large number of other birds, especially North Island robins and fernbirds. Kiwis and land clearance The study focussed on the kiwi because it is probably the most important species in Hawke’s Bay to be affected by land clearance. The region lies at the southern end of the kiwis’ range, and every other bird in Hawke’s Bay that might be affected by land clearance is relatively well represented elsewhere. Lands and Survey’s plan to start clearing the Waitere block from 1983 gave a unique situation for determining the effect of land clearance on kiwis.

While conservationists have argued that clearance destroys kiwi populations, developers have maintained that displaced birds simply move into a habitat nearby. That stance is based on three untested assumptions: that there is in fact habitat close enough for the kiwis to disperse into; that they move out of cut scrub in the six to eighteen month period when it is down drying before being fired; and that kiwis’ territorial behaviour does not limit their density — that they can continue to pour into habitats already occupied by other kiwis. The study was begun in August 1982 to test those three assumptions by radio-tagging birds and following them during the period of land clearance. the plan included uplifting half the kiwis in the central valley, taking them to a reserve elsewhere in Hawke’s Bay, and comparing their survival rate with that of the birds left behind. To date no one has done a follow-up study to find out whether rescuing kiwis from an area about to be cleared is in fact a successful stratagem. The trials of tracking kiwis In practice the study did not go according to plan. First, the difficulty of catching the required number of birds was greatly underestimated. Traditionally, kiwis are caught by playing back a taped call, so that the bird whose territory the fieldworker is in comes up to investigate the intruder. Thus fieldworkers had to go out to different parts of the block each night and plot the positions of kiwis’ responses. On some nights the birds do not call, and it requires up to 20 visits to an area before one can be sure not to have missed a resident kiwi. Birds which are too young to start calling (under 14-20 months) are also missed. In addition, for reasons that are not clear, the Waitere birds do not come in to a call, soa trained dog had to be used to track the birds in order to make the initial capture. In 18 months, only six birds were caught and radio-tagged. The second problem was radio failure. Eighteen radios were put on the six birds in eighteen months. A maximum of three birds had radios at any one time, and for periods there were no transmitters working. Although an enormous amount of time was spent recapturing birds after transmitters failed, radio-tracking still remains the only possible research technique. Little is yet known about the habits of brown kiwis simply because the technology required to study them has only recently become available. The two requirements are radios to keep in touch with the kiwis, and night viewing equipment to observe their behaviour.

Finding Out NOW Many Dirds live at Waitere has been a long and laborious process, requiring bushcraft and physical fitness as well as scientific knowledge. The work has involved two days and nights per week in the field, trying to locate each radio-tagged kiwi during the day to describe their shelters, and at night following them through thick scrub with a direction-finding aerial. A total of 24 birds have been found, but the true population is somewhere between 30 and 50. That represents a possibly unique concentration of kiwis in the region. Another researcher, Mark Robinson, has surveyed kiwis in existing reserves throughout Hawke’s Bay, and has found them in only four reserves, and then only in low numbers. Shelters, activity and ranges There is now good information on four birds — their roosting sites during the day, their activity at night, and in particular the size of their ranges. Locations of 86 daytime shelters were found, and these proved to fall into three distinct types. The simplest makes use of existing cover, where the birds just camp for the day under a clump of bracken. Secondly, they actually excavate their own burrows — females as well as males, although previously it was thought only the males excavated. The third type of shelter is where they take advantage of the natural networks of tunnels which water has scoured out just below the surface of this pumice country. They shelter in a large number of different sites, and normally use different burrows on successive days. However, when they are back in that part of their range again, they will often sleep in a burrow they have used several days previously. Birds whose ranges include a lot of bracken roost mainly under bracken. That fact has important implications for

land clearance. Once the scrub is cut, leaving a dense layer of cover just a metre or so above the ground, the kiwis will probably cease to burrow altogether. In that case, if they are still there at the time of the fire, they will not have a chance of escape. The kiwis’ level of night time activity is astonishing. They emerge at dusk and return to bed at dawn. They are active all night, every night, regardless of the weather. A bird may travel 1000 metres during a single night’s foraging, covering the entire length of its range in a few hours. A kiwi located on one side of its range at 2am has been found on the other side at the end of the night. The birds’ ranges are very large, covering from 14 to 50 hectares. One pair was marked, and they shared the same territory. Also marked were two females, which occupied exclusive territories — although these may overlap with a male’s territory. That result is a surprise, because the only previous study — done in Northland — found territory sizes of 3 to 5 hectares. Large ranges may be a characteristic of the Hawke’s Bay brown kiwis, because birds subsequently radio-tagged in nearby native forest have similarly extensive ranges.

Conclusions The finding on range size is important for the design of kiwi reserves. In the past people have considered that 20 to 50 hectares were probably adequate for a reserve, but we now know that would hold only one, maybe two birds. Taking a minimum viable population to be perhaps 20 pairs, reserves of 500 hectares or more are necessary. Most of the existing reserves in Hawke’s Bay are much smaller. lronically, the Waitere study is being abandoned largely because it has been so successful in finding kiwis. This population and its habitat look valuable enough to merit full preservation, and the Waitere scrub is in any case too dense to allow observation of the kiwis’ behaviour. Research has now moved to an area on the other side of the Mohaka, where a privately owned tract of native forest and scrub called Haliburton’s Bush also holds a significant kiwi population. Ten birds have been identified there, and eight radio-tagged. Their range size and night time activity are proving to be similar to the Waitere birds, while the forest habitat makes fallen logs a frequent daytime shelter. Some research will continue on the Waitere kiwis. A small area of the block is to be cleared this summer, and during the burn-off smoke levels and temperatures in kiwi burrows will be monitored. If a significant portion of the block is cleared, as the management plans proposes, birds will be radio-

tagged, followed throughout the clearance and then, if necessary, uplifted before the burn-off. That research will help answer the key question of whether birds do in fact move out before the scrub is burnt. Waitere contains a viable kiwi population. However, to make it a worthwhile reserve for kiwis, the absolute minimum area that decisionmakers will have to consider setting aside is 500 hectares — and preferably a good deal more. we