ORC, Environment Southland approach drops rook numbers to about 40

Spring is the best time to spot rooks. Photo / Supplied

A joint Otago Regional Council and Environment Southland approach has pushed rook numbers down to an estimated 40 in the South, a far cry from the many thousands which were breeding in the 1980s and 1990s.

Rooks were brought to New Zealand between 1862 and 1873 to control insects but like many other introduced species, their population rapidly exploded.

Over the years, regional councils have been working together to eradicate the pests, with help from the community.

ORC coastal Otago biosecurity delivery lead Simon Stevenson said the work, including the collaboration efforts, community input and dedicated biosecurity teams, had made a massive impact.

"We believe there is no longer a breeding population in Otago because no chicks have been reported in the last six years, which is very good news."

However, the potential remains for the population to flare up again.

For this reason, Stevenson is asking the public to keep reporting sightings this spring, when rooks are most active.

"This enables us to better map nests and target these pests ... We really appreciate the support from the community for our programme over the years.

"It has gone a long way towards the success we have experienced. It shows the success we can have eradicating other pests listed in our plan, for example, wallabies."

Environment Southland biosecurity pest animals team leader Dave Burgess said rooks were not known to be in Southland at present.

"However, populations were evident in the mid-1990s to early 2000s in the Balfour, Eastern Bush and Motu Valley areas.

"During the last 10 years, a small number of rooks have been sighted periodically in the Kaiwera-Pukerau area, thought to be transient birds from nearby Otago areas.

"We rely on reports and sightings from the public which can be done through the councils' PestHub websites."

ORC biosecurity officer Malcolm Allan, who has been in pest control since the 1980s, said he had witnessed the decline.

"We estimate that rook numbers have stayed at approximately 40 birds or less since 2016, which is around half a single rookery held back in the day.

"There is still no evidence of any chicks being born. It's a case of no news is good news, suggesting the rook problem is not escalating.

"But there may be a rookery somewhere that we don't know about and that's why it's so important that the rural sector help us out."

Spring is the best time to spot rooks because it is when they nest.

People are asked not to attempt to shoot at or scare rooks themselves, as there is often only one chance to deal with them.

If they are frightened they can scatter and form new rookeries.

Any control required would be undertaken by the councils.

People who see rooks in Otago are asked to contact the ORC on 0800474-082 or by emailing pests@orc.govt.nz; in Southland: 080076-88-45 or service@es.govt.nz.