Two hen harrier chicks have been rescued after their mother was found dead nearby.
Police in East Ayrshire say the bird of prey's death is suspicious and are appealing for information.
The remains of the adult female were found in moorland near Muirkirk on Tuesday.
Her two chicks were recovered and are being cared for by the Scottish SPCA.
Detective Inspector Graham Duncan said: "While at this time we cannot divulge how the bird was killed, we do believe it was the result of a criminal act and we need to establish why this has happened.
"What is the reason for it? Was it for sheer badness or amusement or perhaps something more sinister?
"We do not believe the bird was lying there for a long time so would appeal to anyone who was in the area - which is quite remote - on Tuesday June 17 or who can assist with our enquiries, to come forward."
Killing a wild bird is a criminal offence under the Wildlife and Countryside Act 1981 and is punishable by a fine of up to £10,000 and six months' imprisonment.
RSPB Scotland warned yesterday that more needs to be done to protect hen harriers during breeding season.
The charity said the population in Scotland is in trouble, with a 20% decline in numbers over a six-year period.
The harrier is a natural predator of the red grouse but the RSPB said techniques such as providing alternative food for them have been taken up by few sporting estates despite their proven effectiveness.
Chief Superintendent Mike Flynn, from the Scottish SPCA, said: "Hen harriers are rare and it is very concerning that someone has killed such a magnificent bird of prey. We can be thankful the two chicks were still alive as they would have died had they not been rescued.
"We are working closely with Police Scotland and would encourage anyone with information to call the Scottish SPCA animal helpline on 03000 999 999 or Police Scotland on 101."
A reward was offered for information on the deaths of more than 20 birds of prey in Northern Scotland earlier this year.
A total of 16 red kites and six buzzards were found in Ross-shire, with tests revealing the majority had been poisoned.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article