The dwindling rook population has resurfaced in Maniototo and about 20 rooks have been spotted on a Kyeburn farm.
The Otago Regional Council is now "keeping an open mind" about rook numbers which were previously thought to have been declining.
The population was believed to have been fewer than 40 less than a year ago, down from thousands in the 1990s.
Council biosecurity and biodiversity team leader Richard Lord said staff had responded to a reported sighting this week and staff were now surveying known rook sites in the area.
"Fog hindered some recent site inspections, but we'll continue the search and will implement appropriate control measures if any are located."