Unborn baby blue penguins are being sacrificed to save their oil-covered parents.
Conservation experts are facing heart-wrenching decisions in the wake of the Rena grounding - and rescuing penguins covered in oil means being unable to save eggs left behind in the nests.
It is breeding season for the 200-300 breeding pairs of little blue penguins in the Western Bay, most of which are incubating their eggs in nests and burrows along the coastline.
However, many parent penguins coming ashore in the evening to find their burrows have crossed rocks covered in thick tar-like oil and become oiled.
Rebecca Bird, from World Wildlife Fund New Zealand, said removing an oiled penguin would give it a chance of survival but would also jeopardise the survival of its clutch.
"We checked on the pair of little blue penguins in the 'window nest' a couple of nights ago and the mate was oiled so we had to take him away to the recovery centre to be looked after. Then the next night we found the other penguin was oiled and had to take her away.
"We hope that the birds we recover will be rehabilitated successfully but it's heartbreaking to know that saving them means their clutch won't be reared," she said.
In an effort to save the clutch, the team placed the eggs with another pair of penguins. But the adoptive pair rejected them.
Miss Bird is one of 140 field staff working as part of Maritime New Zealand's oiled wildlife recovery team, under the guidance of Wildlife field operations manager Brent Stephenson.
He said the decision to save adult penguins and leave the eggs had been tough and many people had a hard time accepting the decision.
"Obviously, it's not an easy thing for people to do but that was one decision we came to, based on all of the research that's around. Adult penguins are a very important part of the population and they have a high survival rate in normal conditions.
"The eggs and most of the young generally die in the first couple of years into adulthood so it was far more important to look after the adults," he said.
The team has been monitoring penguin burrows every day along Western Bay coastline since oil began washing up on Papamoa Beach. It has also focused on the rocky shoreline around Mauao, Leisure Island, Rabbit Island and Maketu Peninsula, where most of the penguins nest.
Miss Bird said when team members found a penguin nest, they evaluated the birds and decided to remove them from their nest and eggs or else marked and checked them the next night. If they were covered in oil, they were taken back to the wildlife recovery centre in Te Maunga to be cleaned and rehabilitated.
Local conservation volunteer Dave Richards said some penguins were abandoning their nests after losing their mate.
"They stay on their nests until they figure out their mate isn't coming back and eventually they'll go and feed."
Last week, Mr Richards and other recovery team members were on Rabbit Island (Motuotau), checking penguin nests. He said they had been "inundated with oiled penguins".
"We were expecting the worst and we found 24 oiled penguins, seven dead, just in the landing bay. It's not so good out here," he said.
"I never thought - it's a relatively small amount of oil - and it's already had such a devastating impact on the penguins.
"It's just heartbreaking."
Mr Richards said this year's crop of young penguins would be much lower than in previous years.
"But the good thing is that mum and dad are being saved and they'll be released when it's safe for them and they can get back to doing what penguins do, having more babies."
More than 300 little blue penguins have been rescued since the Rena grounded on Astrolabe Reef. Miss Bird said their chances of survival were high as they were resilient.