A black-headed gull brought down a drone during a roof survey at a school in Dumfries and Galloway.
The bird attacked the unmanned aircraft system (UAS) over Stranraer Academy around 12.20pm on July 8.
The pilot “had not experienced this level of aggression before” from a bird, an Air Accidents Investigation Branch report said.
Pre-flight checks had been carried out, including an assessment of potential bird interference.
Once the 6.14kg drone was flown manually before the autonomous flight mode was used.
A gull flew from behind and attacked it. The pilot tried to switch to manual control but the front right propeller was damaged and the drone fell on to the roof.
The pilot had previously operated the UAS in coastal and onshore locations where gulls were present.
He had been cautious in those areas, especially during nesting season.