With its sad distinction as England's most persecuted bird of prey, it is hardly surprising that the reported shooting of two hen harriers on the Sandringham estate has been condemned by conservationists, but gamekeepers reject accusations that they are to blame.
The threat to this rare bird is considered so great that at one site in the north Pennines it gets round-the-clock protection.
Hen harriers hunt near the ground, and are relatively easy to shoot
Dave O'Hara, who manages the Royal Society for the Protection of Birds' Geltsdale nature reserve near Carlisle, heads a 24-hour operation when they are nesting at the moorland haven.
"Birds were found poisoned and shot in Geltsdale in the past," he explains, "so we've invested more resources in protecting them.
"We usually have one pair of hen harriers nesting here and a team of staff and volunteers watch it from a distance of about 600m, 24-hours-a-day.
"It can be quite arduous if it is a wet day, but everyone gets a lot out of it."
Tellingly, he adds: "Every year that a nest has been protected, chicks have been fledged in the reserve."
All birds of prey are legally protected under the 1981 Wildlife and Countryside Act. Maximum penalties for killing them are six months in jail or fines of up to £5,000 for each incident.
There is an additional protection for rare species, prohibiting intentional or reckless disturbance when they are nesting.
Conservationists say that after 25 years of protection, there should be dramatic cuts in bird crime.
But the RSPB's latest survey includes 185 reports of shooting and destruction of birds of prey last year - with confirmed shootings of 28 individual "raptors".
It identified Derbyshire, Yorkshire and Northumberland - key areas for red kite, goshawk and hen harriers - as the worst counties in England for such persecution.
There are an estimated 749 breeding pairs of hen harriers in the UK, but England has only 20. Studies indicate there is habitat capacity for at least 200.
The only secure population in England is in Lancashire's Forest of Bowland. Elsewhere there is only sporadic nesting.
The birds fly with their wings in a distinctive shallow "V"
Its scarcity is attributed to routine illegal killing - a taste for grouse making it the enemy of gamekeepers.
"Isn't it sickening that in 2007 we are dealing with practices that were prevalent in Victorian times?" says the RSPB's Grahame Madge of the alleged incident at Sandringham. "I think many of our one million members will be sickened."
He explains that hen harriers are relatively easy to shoot because they hunt by "quartering" low over open ground for birds and small mammals.
"The problem with this type of crime is that it's very difficult to get proof or to name an individual. Even if you see a shooting there may be no body.
"But there was a study in Scotland that looked at golden eagle distribution and that of grouse moors, and it is pretty clear that if you are a golden eagle, you do less well there."
The National Gamekeepers' Organisation (NGO) accepts hen harriers have a very damaging impact on grouse moors, but says the vast majority of gamekeepers operate within the law.
Latin name Circus cyaneus
Distributed across North America, Europe and Asia
Fly with wings in a shallow "V", gliding low for hunting
Males are pale grey, with black wing tips and white rump
Females and immature males are brown with white rump and barred tail
Ground nester, inhabits moors, coastal marshes and reed-beds
"I'm not saying that from time to time a rogue gamekeeper doesn't kill a hen harrier. It must happen, but I think it's a very, very small minority," an NGO spokesman said.
He says he knows of only one case in Scotland in which a gamekeeper was prosecuted and rejects claims that it is difficult to prove the offence when so many resources are thrown at the cases.
The problem is, he says, having hen harriers and grouse on the same moor, so a 10-year experiment is being conducted with conservation groups (including the RSPB) to look at resolutions.
One option would be to provide the birds of prey with supplementary food such as dead rats, he said.
Other options include some form of licensed control which could mean legal culling or catching live harriers and releasing them away from grouse moors, for example in large parts of Wales, Exmoor or Dartmoor.
The spokesman added that there was a general acceptance that grouse moor management is essential for upland conservation, but the hen harrier conundrum needed to be addressed.
Hen harriers are one of only two birds of prey on the RSPB's UK "red list" denoting them as a high conservation priority - the other is the white-tailed eagle - and are also a recognised priority among police wildlife officers and government departments.
The UK has 15 bird of prey species, ranging in size from the small merlin falcon to the white-tailed eagle, which has been reintroduced in Scotland.
And while some are under sustained pressure, the wider outlook is improving.
"What we have seen since the 1970s is a revival in the bird of prey population through better protection, better liaison with landowners, and reintroduction initiatives," says Mr Madge.
"There are now in excess of 1,000 pairs of red kites nesting in the UK, in the 1930s you could count them on one hand. We are also seeing the recovery and recolonisation of osprey.
"We have seen recovery to the point that we now have the same number nesting in Britain as we have ever had - all 15 are in some way resident in the UK. But we believe we have a long way to go to see their full restoration."
Meanwhile, their popularity is soaring with the public - 250,000 people have participated in RSPB bird of prey viewing schemes this year.
"However, it's clear that in some areas if you are a bird of prey you will suffer badly," observes Mr Madge.
"In some parts of the Peak District, for example, there is evidence of systematic bird of prey killing and in some areas, it not possible to see peregrines, hen harriers, or goshawks.
"It's a disgrace because this is one of the most visited national parks in the world. They should be an integral part of the ecology and of the visitor experience."
Some conservationists claim there is an unspoken expectation on many hunting estates that gamekeepers will kill any bird or animal which preys on grouse, or risk losing their jobs.
They want the law changed to permit legal culling when numbers increase.
But Mr Madge argues: "We have the legislation in place. What we need now is the guarantee of enforcement so that we consign bird of prey killing to history where it belongs."