2007/08 season on Stewart Is
Sunday 11th May, 2008
The fifth and final season of fieldwork for the five-year study on Stewart Island has just been completed. In contrast to Year 4, which resulted in 0% breeding success in the monitored area on Stewart Island (the Anglem coast), and lower breeding success on the monitored offshore islands than in previous years, this season was much better. Six chicks fledged from the Anglem coast and 56 and 27 chicks respectively from Whenua Hou/Codfish Island and the Bravo islands, our two monitored offshore island sites. Breeding success was 19% for the Anglem coast, still much lower than the expected average of around 60% (but better than 0%!), while that for Whenua Hou/Codfish Island and the Bravo islands was 76% and 69% respectively. This is the best season of all during this study for these island groups, perhaps influenced by the spectacularly fine summer and La Nina weather patterns experienced this season.
However, it is even more obvious that all is not well for the birds along the Anglem coast. Firstly, only 16 nests were located, compared to 32 nests which were found along the same stretch of coast during the Trust's comprehensive survey of Stewart Island in 1999. That is a very disturbing statistic, showing a considerable reduction in the number of breeding pairs over nine breeding seasons.
Secondly, of the 25 chicks that hatched from those 16 nests, 19 died and only six survived to fledge. All of the chick deaths occurred before Christmas, during the guard phase, and most chicks died within three weeks of hatching.
No predation was recorded, but starvation and disease were once again evident as causes of chick death. Some very detailed examination of chick carcasses was carried out by veterinarians from the Department of Conservation and Biosecurity NZ in an attempt to determine which is the primary cause of death. Provisional results from 15 chicks examined point to starvation as the most widespread cause of death this season. No evidence of disease was found in 12 chicks, but all 12 of these chicks were small and malnourished. The blood parasite Leucocytozoon killed two large chicks which had survived the first three weeks and appeared healthy until a few days prior to death. Only one chick tested positive for diphtheritic stomatitis, although this is not necessarily what killed it as it also appeared to be starving. Other work carried out included the examination of nest material and collection of insects, especially sandflies and mosquitoes, from nest areas to see whether insect vectors may be responsible for the spread of disease. The final report from this investigation had not been completed at the time of preparing this article, and we expect to learn more soon about what the investigation uncovered.
5-year project funding
If the Yellow-eyed Penguin Trust had not undertaken a census of the yellow-eyed penguins on Stewart Island and the adjoining islands in 1999 and 2002, there would have been only anecdotal evidence of their continuing decline. If the Trust had not then embarked on a five year monitoring of the breeding success of yellow-eyeds in selected areas, (2003-2008) the decline on Stewart Island, when it was next measured would have been attributed to feral cat predation, which was our original hypothesis. After the first year, when it became apparent that we needed to make visits more often during the guard stage if we were to be able to get the carcasses soon enough to be autopsied, the role of starvation and disease began becoming paramount, with no sign of predation, especially in the area where cats had been eliminated with a 1080 application. (This was demonstrated by recovery of radio-collared cats in the area.)
Such labour intensive monitoring in a remote area does not come cheap and would not have been undertaken by DOC. The cost per day of staff and overheads during the season amounts to $175.61. This excludes the not inconsiderable DOC contribution.
Since the beginning we have had difficulty raising enough money from grant sources and donations to fully cover the costs and have had to dip into Trust capital funds, to the tune of $63,000, thus foregoing the interest that would have been otherwise used for our general operational costs. Thank you to those of you who have made extra donations and ticked the box indicating that you wished it to go to the Stewart Island Project.
The five year project is now being pulled to a close with the reports being written and another census of all the original coastlines being re-surveyed to see whether other areas have also declined. Depending on funding, it would be good to do this in the coming season. If you can make a donation to assist with the Stewart Island work it would be appreciated. This can be done online through the 'Donate Online' button - put a message in the message box stating this is for Stewart Island work. Thank you.