Four injured Fiordland crested penguins at Wellington Zoo are poised to be returned back to the wild - but only once they graduate from swim school.
The injured birds were brought in separately from the South Island's West Coast over the past six weeks.
Vets at the zoo's clinic The Nest have been putting them through their paces in a saltwater pool to make sure they're ready to head home, where they spend up to 70 percent of their days in the water.
(Simon Wong / Newshub.)
Think of it as a warrant of fitness for birds.
"We have a certain list of criteria that we have to tick off before we say 'yes, they can be released'," vet nurse Deneka De Sousa says.
"One of them is making sure they don't fatigue easily for long periods of time when we swim them.
"The second thing is waterproofing. While they're in the water, we want to see these nice droplets of water which we called beading - a nice formation of water droplets streaming off their back."
The birds sometimes need a bit of coaxing to get into the pool (Simon Wong / Newshub.)
They also want to see the birds preen - using their beaks and natural oils to make their feathers waterproof.
Louis, who was one of the first of the group brought into the zoo, passed his test with flying colours and will be flown back to the West Coast and released on Thursday.
The others - Reggie, Gary and Denny - still need a bit more time before they're fighting fit and can be released into the wild.
(Simon Wong / Newshub.)
It's not known how any of the foursome were injured.
Fiordland crested penguins, or tawaki, are one of three penguin species which breed on the New Zealand mainland.
Despite their name, they can also be found along coastlines south of Bruce Bay in south Westland, the islands of Foveaux Strait and Stewart Island.
(Simon Wong / Newshub.)
Some non-breeding birds have also been spotted in the Chathams, the sub-Antarctic islands and around the Australian coast from New South Wales to Western Australia.
The Department of Conservation says the current population is between 2500 and 3000 breeding pairs, that number dropping since the 1950s.
Newshub.
