Shoppers watched in dismay as a bird of prey hired to clear town centre pigeons killed a duck nesting above a store in Hemel Hempstead.
The Harris Hawk was being flown by a pest control worker in Marlowes, last Wednesday (July 2) when a crowd of adults and children saw it swoop onto a duck's nest.
Witness and former bird sanctuary owner Ray Lindey-Jones, 68, said: "It went straight into the nest and everyone heard the duck scream out."
Mr Lindey-Jones, who said he had worked with birds of prey for about 30 years, added that he thought the pest control company, hired by the council, should have been using a Peregrine Falcon.
"They should never have put a bird like that up there," he said.
Yesterday (Tuesday) however, a fresh falconer from NBC Bird & Pest Solutions arrived in the pedestrianised town centre to fly another Harris Hawk.
Scot Adam, area manager of the firm hired by Dacorum Borough Council, admitted there was a risk of hawks attacking other birds but that the chances were slim.
He said: "At the end of the day they are still wild animals – they're killing machines.
"But we train them as much as we can to only scare birds away."
Mr Adam, from Luton, flew both female and male hawks in the morning and afternoon between Woolworths and Blockbuster in Marlowes and a team from NBC is set to return for eight more straight days after today (Wednesday).
The pest control experts, who specialise in environmentally-friendly methods, will then return one day a week on an ongoing basis.
It is hoped the flights will help to disperse pigeons responsible for causing mess which costs the council thousands of pounds every year to clean up.
According to NBC, which has also helped clear pigeons from Trafalgar Square and Buckingham Palace, pigeon mess contains harmful viruses and bacteria as well as being unsightly.