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So many seabirds . . . Red-billed gulls occupy a section of Sumpter Wharf, in Oamaru Harbour, vacated temporarily by spotted shags yesterday. The Waitaki District Council has been asked to find a "natural nesting location" for the protected species after they inundated Oamaru's central business district again last year. Red-billed gulls are one of seven seabird species that occupy the wharf. PHOTO: HAMISH MACLEAN

Countdown has asked the Waitaki District Council how red-billed gulls can be “attracted back to a natural nesting location”, council communications specialist Lisa Scott says.

A council-led red-billed gulls information session for Oamaru building owners and tenants on June 24 produced “suggested solutions” to the problem-level numbers of red-billed gulls nesting atop central business district buildings last year.

But those solutions would need to go to councillors for discussion, or approval, before being made public, Miss Scott said in an emailed response.

“It was noted [at the meeting] that the gulls have been observed spending more time in the harbour.

“There is a hope that they will be attracted back to the tetrapods. If viable areas in town are eliminated then this would encourage them to move,” she said.

Late last year, Countdown Oamaru said it aimed to have “zero” nests on its centrally located 2000sqm roof space after up to 900 birds nested there last year.

Miss Scott said at the meeting Woolworths New Zealand regional maintenance manager Iain Widlof, representing Countdown, reiterated that target and confirmed that last breeding season, the supermarket’s fourth, had been expensive to remediate.

Hawk calls had proven ineffective; laser cannons were effective only when the laser was moving at speed; and spikes installed on higher vantage points of the roof were effective in conjunction with other methods.

Ozone gas to be trialled this month had proved effective with smaller birds in other areas and loose drift netting would be installed.

“At the worst point of Countdown’s history with the gulls, excrement had blocked the rain heads and guano came into the building causing health and reputational risks,” Miss Scott said.

The council had received advice from the Department of Conservation, but other people at the meeting said ultrasonic sound had been successfully used to dissuade other birds from nesting at a cost of about $3000 to $4000, but gulls could habituate to things that were not physical barriers.

Despite the birds’ “very large population”, Doc’s “Conservation status of New Zealand birds, 2016” report shows numbers of the protected species could fall by up to 70%.

The council’s website warned property owners that red-billed gulls laid eggs from September through January “so you need to put measures in place by July or August at the latest, when they will be looking for attractive real estate to develop and build nests on”.