The Parliamentary Commissioner for the Environment says a rapid decline of unprotected native birds could cause New Zealand forests to fall silent.
Commissioner Jan Wright is investigating the use of the pest control 1080 and its alternatives. Her final report is expected in April this year.
Dr Wright says native birds, skinks and geckos are declining in large parts of New Zealand which are not protected from pests.
She says kiwi numbers in such areas are declining at a rate of 6% a year and predicts their population will be halved in a decade
In future, native birds may be found only on protected offshore islands and mainland sanctuaries, she warns.
Dr Wright says the Department of Conservation may need to re-focus its resources to better protect native birds. At present, it only conducts pest control on about an eighth of the eight million hectares of conservation estate.
DoC says it welcomes the commissioner's inquiry and is awaiting the final report.