Waikato residents are being asked to report sightings of rooks – destructive pest birds which threaten the region’s agricultural production.

The cunning large black birds are bigger than magpies and pose a serious threat to farming as they feed on crops, damage pasture in search of grubs and tear open silage covers.

Information gathered by Waikato Regional Council’s biosecurity team suggests rooks are throughout the region, usually in very low numbers, but more commonly seen in Cambridge, Matamata, Tirau, Putaruru, Mangakino, Miranda and Kaiaua.

Council biosecurity officer Brett Bailey said: “Rooks can be very difficult to find, as they are highly intelligent and can be wary of control methods we employ. The information we get from the public ensures our annual nest poisoning programme is effective.

“Targeting rooks during the nesting period gives us the best chance to effectively control the numbers, but it also means we have a very narrow window of opportunity.”

Mr Bailey encouraged landowners to report sightings of rooks to the council and not attempt to control the birds themselves.

“Research shows that, when free of disturbance, rooks spread slowly. In fact, few young birds will disperse because of their strong attachment to the rookeries of their birth.

“Landowners who attempt to control rooks themselves make the job more difficult for the professionals, as wary rooks will tend to abandon existing rookeries and spread further afield,” he said.

Waikato Regional Council employs professional contractors to control rooks, with helicopters used to access the nests.

Rooks tend to nest high in trees which provide unrestricted views of the surrounding countryside and are situated near waterways.

The birds are natives of the UK and Europe and come from the same family as crows and ravens, which are not found in New Zealand.

The ‘look for rooks’ campaign was first launched by Waikato Regional Council in 2009 and its success relies on information from the public. To report sightings or get more information about rooks go to www.waikatoregion.govt.nz/rook or phone 0800 BIOSECURITY (0800 246 732).