Rabbit Island is again populated by little blue penguins after 49 were released from captivity at Mount Maunganui Main Beach this morning.

They were captured, oiled and in many cases near death, following the Rena container ship disaster in which oil leaked into the sea.

The first penguins to be released into the sea dived through waves.

The oil caused much harm to marine wildlife - killing more than 2000 birds including little blue penguins, shags, wandering albatross, gannet and petrels.

A Wildlife Response Centre was constructed at Te Maunga next to Baypark to house oiled birds – including more than 340 little blue penguins.

Purpose built aviaries were also constructed there and among their inhabitants were about 60 rare dotterel birds.

These were captured prior to their being oiled as a pre-emptive move to preserve the species of which there are only about 1500 alive.

Today's release of 49 penguins back into the wild marks a significant achievement for the Wildlife Response Centre.

It comes after two shags were released on Sunday - the centre's first release.

Wildlife Response Centre manager Kerri Morgan gives a speech during the formalities of the penguin release.

Willdlife Response Centre manager Kerri Morgan says it has been a long process for the penguins who came to the centre covered in oil and will now be able to return to their homes clean and healthy.

'This is what we have been working towards for seven weeks now, since we arrived here on October 5. This is the end of a long journey for these penguins.

"This is the biggest oil reponse effort ever undertaken in New Zealand and it is fantastic to see how our minature city of wildlife can cope. I am both proud and humbled to be part of the response."

The penguins have undergone significant treatment to clean them of the oil and to re-waterproof them.

Each penguin released receives a blood test and veterinary check, and undergoes the 'six hour test” where they are required to swim for six hours without a break to ensure their waterproofing is returned.

All of the adult penguins released today have been microchipped so there can be continuous monitoring of the penguins progress, including tracking of how they breed next year.

'We expect the penguins to head home to their burrows, and as you saw the penguins headed off towards Rabbit Island. Teams will be checking on them each week.”

Kerri says the decision to release the penguins was made after careful consideration and is a balancing act between the threat of another oil spill and keeping the penguins in captivity.

'We understand there is still a threat of further oil leaking from the ship but we can not keep the birds in captivity forever."

Kerri says wildlife experts have thoroughly assessed the area around Rabbit Island in particular where the penguins live to ensure it is suitable for release.

Environment Minister Nick Smith was at the release and says the event is a significant milestone in the recovery of the Rena to date.

'Every New Zealanders heart sank when they saw the images of the penguins covered in oil. This is one of the first steps in the ongoing environmental recovery, that we are all comitted to today, to ensure the Bay of Plenty is restored completely."

Approximately 400 people turned out to watch the birds be released including the wildlife response centre members, volunteers, political dignitaries, Maritime New Zealand, members of the public and three classes of Year 7 students from Bethlehem College.

Oropi resident and wildlife responder Chrissy Jefferson has been working at the response centre since October 7, two days after the ship ran aground on Astrolabe Reef.

'When you have taken a bird that is 80 to 90 per cent oiled and taken them through the wash and rinse process to see them come out all clean is an amazing feeling. You know they are well on their way to recovery.

Chrissy has been working with injured and damaged birds for 50 years and says there is no other feeling like releasing a bird back into its habitat.

'Today is the reason I got into rehabilitation. The feeling you get is like nothing else.”

There are still 290 birds at the wildlife centre in Te Maunga, which will be released in a staged process while the centre is slowly dismantled.

More than 300 people attended the penguin release.

The penguins were confused when they first stood on the beach.

Once they had their bearings, the penguins headed for the water and then swam straight to their original habitat - Rabbit Island.