Takahe in the wild

Forest and Bird, Issue 296, 1 May 2000, Page 14

Takahe in the wild

SHAUN BARNETT reports On survivors in the Murchison Mountains Of Fiordland:

ringing an endangered species back from the brink of extinction is never an easy task, despite the most dedicated efforts of those involved. Since their rediscovery in 1948, the flightless takahe, or notornis, of the Murchison Mountains have been the subject of much research and management. After more than 50 years, scientists are still trying to determine why and how this last population of wild birds was able to survive, when presumed extinct after only four sightings in the nineteenth century. Currently wild birds exist in several catchments of the Murchison Mountains, including the McKenzie, Chester, Woodrow, Ettrick, Point, Mystery and Snag Burns, as well as at the site of their original rediscovery, the Takahe Valley. Over the last two decades an intensive programme of captive rearing and rerelease has attempted to boost numbers. Despite this research, however, some of the key factors influencing takahe survival in the wild are still not clearly understood. Important questions remain over the significance of predators, such as stoats, and other causes of death for eggs and chicks. Even the lifespan and productivity of adult birds is not fully understood. Throw into the equation a potential breeding difference between wild and captive-reared birds and you have a need for more answers. These issues were highlighted in a major review of takahe management completed by the Department of Conservation in 1997. As a result, a significant new study of takahe has recently begun. The 1997-98 field season in the Murchison Mountains was the first of a four-season chick and egg mortality study. Researchers are following the progress of a number of chicks and eggs in the wild. They want to ‘tease out’ the relative importance of predators, nutrition, climate, congenital defects, disease and infections, in bird mortality. Formerly, takahe nests were checked only once or twice during an annual November census, but the new study calls for a more intensive approach. DoC staff have established infra-red cameras and time-lapse videos to monitor a sample of The flightless takahe Porphyrio [Notornis] mantelli amongst alpine tussock in the Murchison Mountains of Fiordland National Park. Sighted only four times during the nineteenth century, the bird was presumed extinct until its rediscovery here in 1948.

nests during egg development. Any dead chicks or eggs are collected, preserved in formalin, and later analysed for infection or disease. Once chicks have hatched, staff use radio telemetry to follow their activities. The use of radio transmitters on takahe chicks was a first for the programme, and required the testing of various harness designs. After initial trials with chicken, pukeko and turkey chicks, a modified "flying bird’ harness design proved to be the most successful. Several wild takahe chicks now sport tiny radio transmitters. Strict handling and monitoring protocols ensure minimal disturbance to both adults and chicks. Last season, video monitoring on four nests did not detect any predators but a stoat plague during the 1999-2000 season may see quite different results. The signif-

icance of predation for takahe is not well understood. Although stoats have been observed killing adult takahe, the frequency of such killing is as yet unknown. Weka taking eggs may be another minor factor. A number of adult takahe die from accidents caused by avalanches, rock falls or simply bad navigation, in the steep terrain of the Murchison Mountains. Unless they are radio-tagged, birds dying from these causes are usually not found. In the past, most takahe have been radio-tagged only in the first year of their life. Using transmitters on birds of varying ages should provide important clues about adult survival rates and the cause of any deaths. One of the key issues of takahe management is a possible difference between the breeding success of captive-reared adults versus wild-reared adults. During 1987-

92 an attempt was made to establish a second breeding takahe population in the nearby Stuart Mountains using captivereared birds from Burwood Bush. (Takahe had earlier been rediscovered in the Stuart Mountains, and the Kepler Mountains too, but these wild populations died out.) Some 58 birds were released into the area, but only a handful now survive. There are several possible explanations for the failure, and one is the poor breeding success of captive-reared birds. Since the attempt, captive-rearing methods have improved, with all releases now made into the source area, the Murchison Mountains. Here survival up to breeding age has been equivalent to that of wildreared birds. The eventual hope is for cap-

tive-reared birds to equal the breeding efficiency of wild-reared birds. Another concern is takahe survival during the harsh winter months, when birds migrate from the tussock tops down into forested valleys. Here they depend on several key food sources, including a plant Hypolepis millefolium. Once the importance of this food source was known, staff at the Burwood Bush breeding facility found they had to teach captive-reared takahe to identify and feed on the plant. Birds released before the significance of this training was realised may have influenced the level of survival of birds in the Stuart Mountains population. The 1999 census revealed some 214 takahe remaining (on rediscovery in 1948 there were about 250 birds). There are

now an estimated 124 takahe living wild in the Murchison Mountains with the rest spread over various protected habitats, including offshore islands (Mana, Maud, Tiritiri Matangi and Kapiti), and conservation facilities at Mt Bruce, Te Anau and Burwood Bush. While most protectedisland populations have increased, numbers in the Murchison Mountains have fluctuated over the period 1981-98. In 1999 there was the first significant increase for the Fiordland birds in some five years (19 percent), possibly helped by the mild winter preceding. There are challenges ahead for the Takahe Recovery Programme, but it seems the right questions are now being asked and answered, and we can look forward to more increases. The aim now is to expand the mainland breeding population into more of its former range.

SHAUN BARNETT is a photographer and writer specializing in the natural world. He is based in Wellington.