Otago's pest rook population falls to 40

A rook. Photo/ORC

It could soon be checkmate for Otago's pesky rooks, as the population is now believed to be fewer than 40, down from thousands in the 1990s.

The Otago Regional Council's season for rook control operations will start next month.

The pest birds were introduced to New Zealand in the late 1800s to control insects, but have been devastating to cereal and grass crops.

Council biosecurity compliance team leader Richard Lord said the council believed "with confidence" there were now fewer than 40 rooks Otago-wide, and there was no longer a breeding population in the region.

There could be "considerably less" than 40, but it was difficult to determine the number exactly, he said.

No chicks or nests had been found since 2015.

The goal was to eradicate them from the region, and the council believed this was achievable, Mr Lord said.

"It may be just due to the ageing population - they may just die out naturally - but we'll certainly control the ones we can."

Rooks were initially established in the Maniototo, Strath Taieri and South Otago.

The main methods of control are poison from ground baiting and poisoning nests using an operator suspended from a helicopter.

Occasionally they would be shot.

The use of helicopter-based poisoning dramatically impacted the Otago rook population when the method began to be used in 1996.

"We still require the community to report any sightings of rooks and the ORC annual programme continues with advertising and site monitoring," Mr Lord said.