Little blue penguins' annual moulting period means some may avoid oiling by hiding in their burrows on the shore.
Oiled wildlife response manager Teri McClelland said penguins went through an annual "catastrophic moult" when they lost all their feathers and then grew them all back.
"The moult takes between 10 and 18 days. When the penguins feel they are soon to start moulting, they start eating a lot to fatten themselves up and then they tuck themselves up in their burrows to wait out the moult," Ms McClelland said.
The penguins have no water-proofing when moulting, so they remain in their burrows and do not go into the sea to feed.
"There's a reasonably long moult season, between December and March. The timing is actually quite good this year, as it means a lot of them are safely tucked away and not going into the water and coming into contact with oil or debris. It's important that people don't disturb the birds while they are moulting," she said.
Ms McClelland said the number of oiled birds - live and dead - being collected around the Bay of Plenty remained small and the oiled wildlife team had been conducting night and day patrols and had found few penguins affected by oil.
"We are receiving a lot of reports of dead birds, but few of them are actually oiled. There is a high natural mortality rate at this time of year, so it could just be that. Many of these birds have just left the nest and are experiencing their first ventures into the big wide world."