Despite there being enough suitable habitat in the English uplands to home at least 320 pairs of breeding hen harriers - last year there were just six successful nests in the whole country.
In an effort to protect nests, the charity has relaunched its sighting line with the aim of finding out where these birds might be breeding.
Hen Harriers are in trouble largely due to illegal persecution. As they sometimes eat grouse, they are illegally killed or disturbed in order to protect grouse shooting reserves.
Earlier this year, the Government and landowners committed to reversing the fortunes of this bird of prey with the publication of the Hen Harrier Action Plan.
Amanda Miller, conservation manager for the RSPB in Northern England, said: “The past few years have been disastrous for England’s hen harriers. We sincerely hope that the new Action Plan will ensure that this season marks a turning point and that we see more of these beautiful birds nesting successfully in the uplands of Yorkshire and beyond.
“I would urge anyone who sees one to report it the Hen Harrier Hotline. As part of our EU-funded Hen Harrier Life+ Project, we have dedicated staff and volunteers ready to protect nests but we can only do so if we know where they are.”
At this time of year, the male hen harrier performs a courtship ritual known as skydancing, which involves a series of aerobatic swoops and somersaults. If he attracts a female, he then proves his worth by passing her food offerings in mid-flight.
Reports can be made to the RSPB’s Hen Harrier Hotline on 0845 4600121 or via email to [email protected] Include the date and location of sighting.