Scientists have been left baffled after a colony of native birds went missing.

The Department of Conservation relocated 30 shore plovers from captive breeding facilities to Mana Island in February.

Since then, the birds have flown back to the mainland, spreading out across the Wellington Coast.

DOC's Troy Makkan says they aren't one hundred per cent sure why.

"There may have been one strong bird that took off and the other followed - but we're also considering avian predation."

Makkan says earlier this week they caught the last three believed to be alive.

'Every bird is really important and the predation from cats, rats and stoats on the mainland means they're disappearing rapidly."

Only 250 shore plovers are left in the wild.

LISTEN ABOVE