The Dunedin City Council has confirmed its plan to spray southern black-backed gulls with non-toxic coloured dye to monitor their dispersal from Green Island Landfill is being reviewed.
A council spokesman said the dispersal operation was yet to begin, but a trial of various techniques was completed last month.
"The results are still being evaluated but will help us update our black-backed gull management plan.
"The need for colour marking will also be reassessed as part of this work."
The council plans to lower the number of the superabundant native birds in the city from 10,000 to about 5000 over the next five years in order to allay aviation safety concerns at Dunedin Airport when the landfill stops accepting food waste and ultimately closes.
The Green Island landfill was a major food source for the birds and in July last year, 8320 birds were counted there, the council’s draft management plan said.
The council has applied to extend the consents for its Green Island landfill for up to seven years and the draft plan was submitted as part of that application.
The plan said 10 birds would be tracked with GPS devices and a large number of birds would be sprayed with non-toxic food-grade dye for a three-month dispersal period.
Staff would turn sprinklers on and mist the birds for a couple of hours each day to get them accustomed to being covered in water droplets.
Then, a small amount of coloured dye would be added to the solution to colour-mark the birds and assist with monitoring them.
The draft plan said in June, July and August this year, and then April, May and June next year, a team of trained wildlife staff would use a range of tools — from a gas cannon, starter pistol and pyrotechnics to kites, balloons and arm-waving to disperse the birds from the area.
The plan has won favour with the SPCA for its non-lethal methods of population control.
