Six birds of prey were found dead near Inverness prompting an investigation by police.
Police Scotland officers from Ross-shire and the force’s Highlands and Islands Division are carrying out enquiries after five red kites and a buzzard were found dead.
The raptors were all found within the Conon Bridge and Muir of Ord area of Ross-shire between Monday, March 17, and Monday, March 24.
DI Scott McDonald, who is leading the investigation, said: "At this time we are unclear as to what has caused the death of these birds but given all the circumstances and the close proximity of them being found we must assume at this stage some form of criminality.
"I would ask anyone who has been working on the land or using the area for recreational purposes to contact us if they have seen anything suspicious that may be linked to this incident."
Douglas McAdam, chief executive of Scottish Land & Estates, said crime against wildlife "would not be tolerated".
He said: ““If there is found to be some form of criminality involved in the deaths of these birds of prey then this is something that we would wholeheartedly condemn.
"Wildlife crime of any kind will not be tolerated by the responsible majority.
“Scottish Land & Estates will continue to do whatever it can to help eradicate all incidents of wildlife crime."
Scottish Gamekeepers Association Chairman Alex Hogg added: “This is a hugely disappointing discovery and the SGA condemns wildlife crime."
If anyone finds any further dead birds in the area they are asked to make a note of its location and inform the police but not to touch or attempt to recover the birds.