England's most endangered bird of prey remains vulnerable despite a record number of fledglings this year, conservationists have said.
Record fledgling numbers may not be enough to save hen harriers
English Nature said 46 chicks hatched this year in 12 nests.
But the breeding was limited to one area - in the Forest of Bowland in Lancashire - and the species was still threatened by persecution.
The hen harrier is disliked by many estate owners because it eats red grouse chicks.
English Nature said its population was a "pale shadow" of what it could be.
About 60% of nesting attempts had failed away from the area that English Nature and the Royal Society for the Protection of Birds (RSPB) monitored.
Richard Saunders, the manager of English Nature's hen harrier recovery project, which has been monitoring the bird since 2002, said grouse shooting had nevertheless contributed to the protection of some of the nation's rarest habitats.
"Monitoring such a beautiful and fascinating bird over the last five years has provided me with many wonderful experiences," he said.
"At times though witnessing the effects of persecution has also been thoroughly depressing.
"There is evidence of illegal persecution every year and we cannot tolerate or ignore this happening to such a rare species."
He called for gamekeepers and land managers not already involved in the project to join conservationists in efforts to build up the population of the species.
This autumn, new conservation body Natural England will take over from the Countryside Agency.
The RSPB's director of conservation, Dr Mark Avery, said Natural England would need to put effort and money into stopping the illegal killing of hen harriers "if this bird is to get back where it belongs - on the nation's moors".