Diving Petrels nest on Motuotau in the hundreds. These birds were particularly vulnerable to the Rena oil as they fly close to the surface of the water and sometimes fly through waves. Around 2002 pest-free Motuotau was invaded by a stoat which killed nearly 100 birds in a short space of time. The stoat was trapped by DoC. Some birds have been banded with metal bands during the 1990s were still alive in 2011.
They are trying to re-establish themselves on Mauao and Moturiki but struggle against cats and stoats that easily catch and kill them.