Environment Southland recently received a report of three rooks seen on farmland between Mossburn and Five Rivers.
Biosecurity officers completed inspections of the properties involved and have been unable to confirm the presence of the birds so far.
Biosecurity and biodiversity operations manager Ali Meade said the public played a vital role in helping keep rooks out of the province, and people were encouraged to report all potential rook sightings to Environment Southland.
"Rooks are pest birds in Southland, and it is essential that sightings of any number are met with a swift response," she said.
"We are grateful that a vigilant member of the public reported the sighting of three rooks in northern Southland so that our biosecurity team could take action."
Environment Southland asked the public not to attempt to shoot or disturb rooks.
Instead, it asked for sightings to be reported immediately so a rook control specialist could be called in, at no cost to the landowner.
Rooks are an exclusion pest under the Southland regional pest management plan.
They can be identified by their fully black feathers, which can have a purple gloss.
Rooks are slightly larger than magpies and also have a distinctive repeated "caw" as their call.
Rooks can cause serious damage to farms as they feed on most types of crops, either removing seed heads or pulling out young plants.
Rooks were brought to New Zealand between 1862-73 to control insects, but like many other introduced species, their population rapidly exploded.
In recent decades, Environment Southland has worked with its communities to eradicate the pests.
Sightings of rooks can be reported through the Environment Southland website or by calling Environment Southland.
