The bodies of five red kites and a buzzard have been found in the Muir of Ord area of Ross-shire in the last week. The birds of prey were found dead at several different nearby locations.
Police Scotland it that at this stage in the investigation it was not clear how the birds died, but said it was likely the deaths involved “some form of criminality”.
Det Insp Scott McDonald said: “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.”