Two male hen harriers have disappeared in suspicious circumstances from the RSPB reserve near Carlisle.
Police are investigating the incident at Geltsdale and are appealing for information about their disappearance.
PC Samantha O’Key the force’s wildlife, rural and environmental crime co-ordinator said: “The two male birds were servicing nests, and as a result both nests have now failed.
“In 2020 another male bird went missing in suspicious circumstances.
“The male was servicing two nests and as a result both nests failed. These birds were in good health, in a perfect environment for them to thrive, with plenty of food. It is highly unlikely that the harriers have died of natural causes.
“Hen harriers are a Schedule 1 protected species under the Wildlife and Countryside Act 1981, and are one of the UK’s most persecuted bird of prey.
Warden at RSPB Geltsdale, Steve Garnett added: ” “This is devastating news, for hen harriers, for our hard-working team here at RSPB Geltsdale and for everyone who is rooting for a better outcome for these birds.
“Each season, the joy of seeing these birds return to breed is always tinged with worry over what might happen to them while they’re hunting beyond the safety of our reserve.
“We can make sure they are safe when they are on our land, but of course, they are free to range more widely and we know that not everyone has the best interests of these birds in mind. Hen harriers are illegally killed every year, so we are bound to view these disappearances as suspicious.”
Anyone with information can contact the RSPB in confidence on its raptor persecution hotline 0300 999 0101, Cumbria police on 101 or Crimestoppers anonymously on 0800 555 111.