The cost of ridding London's Trafalgar Square of pigeons has cost residents more than £130,000.
More public events have been staged in Trafalgar Square.
Figures revealed by the Lib Dems showed that last year it cost £28 for each of the 4,900 pigeons removed.
A Harris hawk was hired at a cost of £106,000 to scare off the birds while £30,00 funded a scientific study into feeding the pigeons.
The Greater London Authority said the initiatives had reduced the pigeon's population to 100.
Mike Tuffrey, the Liberal Democrat Environment spokesman for the London Assembly, said the extra costs meant Londoners would continue to suffer from huge increases in their council tax bills.
"While there is no disputing that the pigeons in Trafalgar Square were both a nuisance and a health hazard, serious questions must be asked about how on earth a hawk costs £105,000 to hire for a year.
"It is a nonsense that so much cash is paid for the use of a bird. "
Mayor of London, Ken Livingstone said the success of the programme meant its costs were now declining sharply.
"The cost of the hawk has actually fallen from £105,000 last year to just £25,000 this year.
"The programme has been successful in reducing the pigeon population in a humane way from some 5,000 pigeons swarming over the square in 2000 to a more manageable 100 this year.
"As a result of the pigeon-reduction programme, major cleaning of many of the statues and flagstones on the square has not been required, saving the taxpayer from having to clean up the huge and unpleasant amounts of pigeon faeces on a regular basis."