Horrified officer workers have appealed to managers of the Nicholsons Centre to stop the killing of pigeons in the High Street.
But bosses say it is a 'last resort' to try and deal with the mess they create.
People working in Nicholson's House were appalled when they looked out the window and saw the birds being strangled.
A pest controller has been called in to cull them because centre owners are sick of the building being covered with bird mess and carcasses.
Traps have been set on top of the centre above Ernest Jones and each day up to 15 pigeons are caught.
Ten Group's offices are on the sixth floor of Nicholson's House overlooking the rooftop.
Lifestyle manager Ashleigh Braund said: "It is a horrific sight.
"We have to watch these birds stuck in the cages for up to eight hours and then to top it off we see them get slaughtered."
She appealed for the killing to stop and suggested artificial nesting sites are set up so the birds' eggs can be collected.
Operations manager at the centre Howard Lindsey said: "I understand people might get upset but this is pretty much our last resort.
"We have tried spiking and netting but it doesn't work.
He said two of the traps had been moved from people's view and the culling would run on a trial basis until next month.
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