Oi back on Auckland mainland after 50 years

Nature lovers who spent years raising money for a pest-proof fence have been rewarded with the return of the Oi.

The Oi - or grey faced petrel - has been spotted nesting on the Auckland mainland for the first time in about 50 years, having spontaneously decided it was safe to come back.

A few years ago, seabird chicks would have been eaten in their burrows by rats and other warm-blooded predators.

But volunteers worked with Auckland Regional Council to replant, fence and kill predators at the tip of the Tawharanui Peninsula, and opened a "mainland island" sanctuary there in March 2006.

Seabird researcher Chris Gaskin was listening for bird calls to find out which birds had re-settled there when he heard the Oi's distinctive cry.

A ground search uncovered several burrows built by petrels - including one containing a peeping chick.

Volunteer Jan Halliday said bellbirds returned quickly after pests were killed when a "few strays" from Little Barrier island expanded to a population of 700.

Kakariki had been deliberately re-introduced, and a few hihi and kaka had also found their way back. But seabirds had remained absent, until now.

Mr Gaskin said the return of the Oi was significant because seabirds played an important role fertilising soil on the mainland with nutrients from the sea. The absence of seabirds was a sign the ecology of the area was "broken".

Petrels feed at night, mainly on squid and fish, and lay their eggs in June and July.

The new chick will be ready to leave the nest in December or January.