Conserving the KAKIRORI

Forest and Bird, Volume 15, Issue 3, 1 August 1984, Unnumbered Page

Conserving the KAKIRORI

and

Rod Hay

Gerald McCormack*

Deep in a few remote valleys of Rarotonga, sharp staccato cries signal the presence of one of the world’s rarest birds. The species is the kakirori, or Rarotonga flycatcher (Pomarea dimidiata), a member of the large family, the Muscicapidae. This group comprises 328 species in all, including our New Zealand robins and tomtits which this bird superficially resembles, with its large eye, whisker-like protruberances around the base of the bill, and confiding nature. Colour polymorphism The amount of raucous noise that these birds make belie their size. About a third the weight of a song thrush, the species comes in two colour-schemes. While most are slate-grey above with pale grey underparts, a small proportion (two out of sixteen seen recently) are a rufous or ginger colour giving them an appearance not unlike that

of an orange canary. Perhaps the species provides another example of the colour polymorphism seen in the black and pied forms of the fantail. Though six kakirori were collected in the 1860s by Andrew Garrett, there were few others seen subsequently and it was clear that the species was rare by the early 1900s.'In fact, the Dictionary of the Maori Language of Rarotonga, written in the 1940s by Stephen Savage, classified it as extinct at that time. Not extinct after all After sightings of five individuals by David Holyoak in 1973 and of the same single bird by Euan Cameron and by Graham Turbott in 1982 and 1983 respectively, English Ornithologist, David Todd last year trekked many of the valley systems of the island and made definite sightings of 21 birds,

including two pairs that were nesting. Now, the kakirori provides us with some hope for its continued survival. Because little is known of habitat requirements or behaviour, more study is urgently needed. With this in mind, we have colour-banded birds in one locality, to enable systematic data on nesting and habitat use to be gathered over the next breeding season. Possible reasons for rarity Why is the kakirori rare? Rarotonga’s montane forests are largely unchanged by browsing mammals, fire or timber extraction. Perhaps, therefore, predation has had an effect, legacy of the almost Pacific-wide introductions of rats (Polynesian, Norway and ship species), cats or mynas. The ship rat (Rattus rattus) is an abundant feature of the forest and it has undergone dramatic fluctuations in numbers in the past. For example, in 1918, Rarotonga was experiencing a serious rat plague and Resident Commissioner reported paying out 600 pounds in ‘‘penny a tail’’ bounties but commented that ‘‘they are as numerous as ever’. As in New Zealand, and on some of our offshore islands, rats may be an important limit to the bird’s recovery. Feral cats are found in moderate numbers according to locals. If, as on Little Barrier Island, they favour the drier ridges and spurs, then that could explain the current restriction of Kakirori to the bottoms of deep valleys. Who would have expected the dramatic recovery of stichbirds after the removal of cats from Little Barrier when there had been no direct evidence of predation? Perhaps a similar situation exists on Rarotonga, an island which invites close comparison in vegetation and topography. The Indian myna (manu kavamani), or "government bird’, named after its early introduction to control insect pests) is easily the most abundant of Rarotonga’s birds, occurring in remarkable densities on the cultivated coastal strip of the island. Mynas also occur in the forest, but not in such high densities. It has been suggested, that they will prey on nestlings and eggs of

other species and that they could bea major reason for the kakirori’s decline. The idea that habitat is restricted stems from the current distribution of the birds and from the fact that the coastal strip of the island is entirely cultivated. Perhaps they used to occur there. It appears, however, that this area has been cleared for hundreds of years and that the kakirori has undergone a decrease in numbers during European times in inland habitat that has remained essentially unmodified. Though the foregoing explanations are speculative, they under-line the need for further research on this bird. What needs to be done and what is proposed? Firstly, volunteer assistants will follow the fate of nests during the current breeding season. Habitat use and area requirements will be studied in one catchment with reference to the eight birds that we have just colourbanded. Finally, survey of the few areas not so far investigated will be undertaken using playback of recorded calls to determine more accurately the size and extent of the population. It is not anticipated, however, that there will be many in excess of 30 birds. Future work It is gratifying that the International Council for Bird Preservation is considering funding a full study. Comparative work could then also be carried out on the other endemic Rarotongan species, the starling (Ap/onis cinerascens), a bird whose reduction in numbers also gives cause for concern. Officials of the government of the Cook Islands have shown enthusiasm for this type of work, and we understand that plans for development of parts of the island for growth of fuel-wood will not jeopardize those areas necessary for the survival of the important endemic birds. Acknowledgement must be made of the assistance given so far by the Cook Islands Government, particularly by the Permanent Secretary of Internal Affairs, Mr Tony Utanga, by the Department of Scientific and Industrial Research, South Pacific Regional Environment Programme, Forest and Bird and ICBP. , a