A $300 reward is being offered for sightings that lead to the capture of a bird threatening New Zealand's native birds, and fruit and vegetable crops.
The Department of Conservation (DOC) believes there are at least five red-vented bulbuls in Auckland, which it says are one of the most invasive bird species on earth.
DOC is offering the reward to anyone who provides information that leads to the capture of one of the birds.
"These prolific breeders have been found in Auckland twice before and successfully eradicated. They're back and we need to act fast to ensure they don't have time to make themselves at home,'' spokeswoman Liz Brooks said.
The payout will go to the person who provides the first sighting that directly leads to a successful capture.
The birds are thought to be located in three clusters: in south Auckland (Manurewa, Alfriston), west Auckland (Henderson, Te Atatu, Massey), and on the North Shore (Devonport, Belmont, Takapuna, Whangaparaoa Peninsula).
There have also been unconfirmed sightings at Orakei in central Auckland and at Walton in Waikato.
Anyone who spots a red-vented bulbul was asked to call 0800 80 99 66 and provide the location of the sighting.
People were also asked to take a photo if possible.