Another 38 clean little blue penguins are joining 56 other birds in returning to their normal nesting grounds following the grounding of the Rena.

The penguins were released at Mount Maunganui on Monday, November 28, following the first release of 49 penguins on the beach last Tuesday, November 22.

The first release of clean little blue penguins on Mount Maunganui beach.

Four other penguins were released into their usual habitat at Waihi Beach on Saturday, November 26 and the last two shags still at the Te Maunga Wildlife Centre were also released at Mount Maunganui in the weekend.

More than 340 little blue penguins were housed at the wildlife centre in Te Maunga following the oil leak from the stricken cargo ship Rena, grounded on Astrolabe Reef since October 5.

National Oiled Wildlife Response Team coordinator Kerri Morgan says there are 240 penguins still at the wildlife centre, while their habitats are checked to ensure they are clean enough to return them to.

With no oiled birds found in the last three of weeks, intake sections of the centre are being 'minimised” but can be ramped up quickly if there is another spill.

'Only a small number of oiled birds have been found in the last few weeks, but we are still looking.”

All birds released went through a thorough process of having blood taken and ensuring they were able to pass their six hour continuous swimming test, as well as having the salt in their swimming pools increased to ensure they could tolerate returning to salt sea water.

On Saturday night a team searched the Mount Maunganui area and checked 87 birds, which were not oiled, microchipping all those found so they could be monitored.

The birds provide an opportunity to study two populations of penguins during the next few years – those that have been rehabilitated and released, and those unaffected by oil.

'We will be able to follow them to see what happens to breeding patterns and other factors.”

To date, 150 birds have been microchipped and released, and a team is headed to Rabbit Island today to do a post-release survey of the released birds to see if they have returned to their usual homes.

'These birds have high ‘site fidelity', which is why we can't release them until their habitat is cleaned.”

Forty-three New Zealand dotterels are still captive at the Wildlife Centre, after 17 were released on Friday. The remaining birds' habitat still has to be cleared before they can be returned. People who find oiled birds, dead or alive, please call 0800 333 771.

Meanwhile, 26 containers were removed from the ship on Monday, bringing the total number of containers lifted from the Rena to 145.