Veterinarians caring for a Royal penguin found thousands of kilometres from its Antarctic home say the bird has a 20% to 30% chance of survival.
The bird, thought to be no more that one year old, is being treated at Wellington Zoo.
Royal penguins are usually found on Macquarie Island, more than 2000km away from New Zealand, and at least 20 degrees Celsius colder.
Wellington Zoo veterinary science manager Lisa Argilla said the bird's condition is improving - but its survival will be touch and go.
If it does survive, Dr Argilla said it will need about six weeks to return to full health.