The chick had entered a ceiling vent at Royal Aberdeen Children's Hospital – where it died.

The carcass attracted maggots which then fell into operating theatres.

Infections expert Prof Hugh Pennington said the blunder at the state-of-the-art hospital "made staff look foolish".

He added: "Someone in for surgery has a right to expect the operating theatre to be the cleanest place in the hospital."

"Birds nest on roofs, but you take precautions to make sure they don't get inside."

Three theatres closed and ops were cancelled last week after cleaners found 25 maggots.

NHS Grampian said they have no idea how a bird entered the vents on the building, which opened in 2004.

An spokesman added: "The pipes will be sealed with wire mesh to stop more getting in."