Yellow-eyed penguin nest numbers have reached their lowest since 1990 and the Department of Conservation (DoC) says the breeding season for the birds is looking bleak again this year.
Nest numbers in the Otago-Southland region have dropped from 491 pairs in 2012 to 160 counted this season.
Numbers are estimated to be less than 190 after all nesting sites have been searched.
"What we are seeing on the mainland is a significant reduction in breeding stocks, with negligible recruitment of young birds," DoC Coastal Otago biodiversity ranger Mel Young says.
Breeding adults have been the hardest hit in the past three years by events such as widespread starvation, outbreaks of avian diphtheria in chicks and unexplained mass mortality assumed to be from a toxic agent.
"The cumulative nature of multiple mass mortalities is coming home to roost. Every bird is important, and we are doing our utmost at each site," Ms Young says.
DoC will work with the Yellow-Eyed Penguin Trust (YEPT) to patrol monitoring areas and beaches to ensure the birds are in good condition. Underweight or injured birds will be removed for treatment and rehabilitation.
Further south on Codfish Island, YEPT reported 33 nest numbers - one up from last year.
Codfish Island is a predator-free island but numbers have still declined significantly over the past 10 years.
"Finding a chick marked from the 2011/12 season is the first evidence of recruitment since the 2007/08 season, but it is insufficient to keep up with normal mortality rates," YEPT general manager Sue Murray says.
"No juveniles have been seen, so none of last year's chicks are likely to enter the future breeding population."
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