KEY POINTS:
All but one of the yellow-eyed penguin chicks hatched on Stewart Island this breeding season have died, from a mystery illness that has veterinarians scratching their heads.
Massey University is investigating the cause of death which has wiped out 31 chicks aged between five and 10 days.
The Yellow-eyed Penguin Trust said this year's breeding season was the worst since monitoring began four years ago, when it began its five-year research programme into the island's declining penguin population.
Disease has ravaged already-endangered yellow-eyed penguin populations for the last few breeding seasons.
In 2003, several newly-hatched chicks died of a mystery illness on Stewart Island.
In 2004, avian diphtheria disease killed about 50 per cent of chicks born throughout the country, except at Katiki Point, near Palmerston, where an intensive antibiotic-treatment programme resulted in only two deaths in 33 chicks.
The disease was detected again last year, but in much smaller numbers.
This year, Dr Andrew Hill, a wildlife vet at the university's Institute of Veterinary Animal and Biomedical Sciences, spent two weeks on Stewart Island collecting blood samples, and another week on Southland's Caitlin Coast studying the population there.
He said the Caitlin coast population looked healthy.
The chicks' symptoms and samples point to one of two conditions -- a blood parasite transmitted by sandflies which destroys red blood cells and leaves chicks weak and vulnerable to infection; or an avian mouth disease which affects the chicks' ability to feed.
- NZPA
