Dead pigeons found floating in Peterhead harbour were killed humanely, the Scottish SPCA has said.
An inquiry had been launched after about 40 were found earlier this week, although there may have been as many as 100 in Albert Quay.
The charity said post-mortem examinations on three of the pigeons shows their necks were dislocated and they should not have suffered.
This is said to be a recognised legal method of pest control.
Scottish SPCA senior inspector Scott Elphinstone said: "How whoever was responsible managed to contain these birds and how they came to be in the water is another matter.
"But we are at least satisfied that the post-mortems have concluded there was no suffering.
"We would however caution that this method of humane destruction should only ever be carried out by experts and that anyone doing so without the appropriate knowledge and who caused animals suffering would be committing an offence."