The Otago Regional Council is calling for reports of the pests, which damage crops and pasture, so they can be eradicated.
The council's regional services group manager, Jeff Donaldson, said so far this season rooks had been reported in Greenfield and Wairuna in South Otago, Moeraki in North Otago and in the Macraes-Nenthorn area.
"Unlike most years, there have been no reports of rooks in the Strath Taieri area so far, bucking the recent trend, but some have been seen in the Maniototo."
Regional services were interested in every sighting and were especially keen to locate any new nesting sites, Mr Donaldson said.
Last year, rooks were reported in central Balclutha and on the Otago Peninsula.
"The response we got last year was the best we have ever had."
People who saw a rook on their property should not shoot at or scare the birds as there was often only one chance to deal with them before they scattered, Mr Donaldson said.
There was no cost to landowners for their eradication, which had enabled the population to be reduced to about 120 rooks.
People noticing rooks are asked to phone Malcolm Allan on 027-278-8498, or the Otago Regional Council on the freephone number 0800-474-082.
Rooks
- Part of crow and raven family
- Larger than magpies
- Totally black with purple or bluish sheen in bright light
- Introduced from Europe to control insects
- Cause damage to crops and pasture