Birdwatchers last saw the chicks, aged four to five weeks, at the beginning of June. The adult birds have now left the nest.

Peregrine falcons can fetch up to �3,000 on the black market and it is believed the chicks may have been stolen for sale in Europe or even for rich Arabs who place a high value on Scottish wild birds.

The theft has prompted a move to ask the Scottish Parliament to consider giving more protection to rare birds.

Three chicks were stolen

This latest incident is the fourth time in six years that breeding peregrine falcons have been targetted at Torphin Quarry.

Peregrine falcons started returning to sites in 1994 after an absence of 15 years.

Lothian and Borders Police Wildlife Liaison Officer for the West of Edinburgh, Roddy McIntyre, hopes the adults will return.

"We waited a long time for peregrine falcons to return and I'm confident they will come back next year but we need the help of the public to prevent this crime happening again," he said.

"Next year we hope to have security measures in place but it's the public who can help most.

RSPB Scotland spokesman David Minns said: "It is tragic that these spectacular birds should come right back to the edge of Edinburgh to nest and then fall foul of selfish people who put their own profit before the Scottish people's enjoyment of their natural heritage.

Call to parliament

"We know that the vast majority of people want to see these birds flying free and will do everything thay can to support the excellent work of the police wildlife liaison officers and their network of volunteer helpers.

"RSPB Scotland will be pressing the Scottish Parliament to review the law protecting these birds, with a view to tightening it up and making it easier for the police to bring those who commit wildlife crime to justice. It must not be allowed to continue increasing as at present."

Peregrine falcons and their nests and eggs are protected under the Wildlife and Countryside Act 1981, which allows for a maximum fine of �5,000 for anyone convicted of interfering with them.