Taking to the air has proved the best way to tackle an avian pest that can significantly harm farm production.
Last week Waikato Regional Council contractors used an applicator dangling from a helicopter to place poison in five rook nests at Lake Te Ko Utu Park in Cambridge.
Rooks were originally introduced to New Zealand to control grass grub but are now classified as a pest under the council's regional pest management plan.
"They are a classified as a production threat as they feed on newly sown crops, especially the likes of cereals, peas and maize, and uproot young plants to get at the seed," says pest animals biosecurity officer Paul Quinn.
"They also damage pasture searching for grubs and interfere with silage by ripping up the plastic wrap."
Cambridge has been a key centre where rooks form breeding rookeries.
"We have had sightings of up to 18 rooks in Cambridge, with five nests at Te Ko Utu Park in the gum trees behind the tennis courts," says Mr Quinn.
The council generally undertakes rook control in spring with contractors applying toxin directly to the rook nest.
"It is highly effective at reducing rook numbers."
The toxin is less toxic to other birds and to help minimise potential harm to non-target species the council removes any dead birds.
Members of the public are advised not to handle any dead birds and to keep dogs on a lead.
In the wider region, rook numbers are currently low, with the birds present at just six known sites.
- However, council is interested in any sightings. They can be reported to council on 0800 BIO SEC (0800 246 732).