A record number of hen harrier chicks have been fitted with satellite tags this year as part of a conservation project.
The RSPB said more than 30 young birds have been fitted with transmitters in the UK so far, up from 24 last year.
While the conservation charity said it could not reveal the exact number as part of efforts to protect the species, most of the newly-tagged birds are in Scotland, with a number of them the offspring of birds tagged in previous years by the project.
Hen harriers are one of the UK’s rarest birds with a population decline due to habitat disturbance and illegal killing, according to the RSPB.
The charity hopes that by tracking the movements of the threatened birds of prey, it builds up a clearer picture of where hen harriers go and where they are at risk.
Of the birds tagged in 2017, almost 40% are known to have died from natural causes, in line with low survival rates.
The charity said that over a quarter of last year’s chicks disappeared in suspicious circumstances, with transmissions from tags suddenly stopping around grouse moors.
The latest national survey of hen harriers, carried out in 2016, found the UK population has declined by 24% since 2004.
Dr Cathleen Thomas, project manager for the RSPB’s Hen Harrier Life project said: “Satellite tagging technology has taught us so much about the movements of hen harriers.
“We can follow individual stories, from the birds that make huge journeys crossing over seas to those that stay closer to home and only move short distances from where they were hatched.
“We’ve discovered new nesting places and winter roosting sites, which help us protect the birds when they are at their most vulnerable.
“The tags also allow us to investigate where and in what circumstances these hen harrier chicks are lost so we can better understand how to protect them and advocate for licensing of driven grouse shooting.
“This species is only just holding on in the UK; it’s both heart-breaking and infuriating that year after year many of these chicks disappear in suspicious circumstances.
“The loss of birds in this way is both needless and senseless and cannot go on.”