If Prince William wants to be a conservationist, then he must stop shooting

Here's a little tip if you want to get on in public moralising: don't lecture the world on tidiness in dress if your flies are undone. This chunkette of worldly advice is particularly useful this week to Prince William. Like many a royal before him, he has taken up the cause of wildlife conservation – and it's a damn fine cause too, so good on him.

The Prince has been in America talking about elephants and rhinos. It's reckoned that 35,000 elephants get poached every year for their ivory and 1,000 rhinos for their horns. He advocated a zero-tolerance policy on this. He spoke about the need to deal with the transport industry across the world, starting in our own country: "Criminals are able to exploit weak and corrupt standards, so we must raise standards collectively."

Flawless. So far as it goes. It's an international problem that needs an international solution and if he can get a royal name and the American President on the same side as the elephant and rhinos, he will have done a fine thing.

But here's a thing about conservation: it's global. That doesn't mean foreign. It means it's a domestic issue as well as a foreign one. You can't go to Brazil and tell them not to destroy the rainforest if you support the destruction of ancient woodland for the High Speed 2 rail route.

Conservation doesn't start with telling foreigners what to do: it starts with doing the right thing yourself. If you're in a public position, you should being doing the right thing loudly and clearly.

That consistency has eluded Prince William. It has eluded three generations of royals, all very keen on conservation, but whose work for wildlife has been compromised by their taste for killing it. Prince Philip's 15-year spell as president of World Wildlife Fund remains a good joke in conservation circles; Prince Charles's advocacy for wildlife has been hampered by his lifelong taste for hunting and shooting.

And so it continues with Prince William. If he wants to be taken seriously as an advocate for conservation – rather than a good-hearted meddler – he must speak out against the grouse-shooting industry in Britain. As it is, he's been a participant.

Grouse-shooting is legal, but in recent years it has become industrialised. The Economist reckoned it cost £3,000 per person per day to participate in a shoot in 2011. There was happy talk of record bags this season – 3,000 grouse shot over four days on one estate and so forth.

Such bags are made possible by hyper-intensive management that includes the routine killing of birds of prey. Let's not get emotional about this: let's get legal. Killing birds of prey is against the law. So it's not a good thing for a future king to be associated with. Grouse-shooting has plenty of rich, powerful, well-connected defenders who ignore the facts and say conservationists are being unreasonable. As if the law didn't apply to them.

I'm not opposed to shooting. I'm opposed to breaking the law. Fact: there is room for 300 pairs of breeding hen harriers in England, according to Defra. Fact: in 2013, not a single pair bred. Four pairs managed to do so this year. In Scotland, hen harrier numbers have declined – and by one of those Nostradamus-like coincidences, the places where their numbers have declined most steeply are grouse moors.

This is becoming a political issue. There was a march in London last week – Rally for Nature – which carried a lot of anger about the killing of hen harriers. It comes down to a single question: whose countryside is it anyway? Do we all have a stake? Or is it just for a few rich and powerful men who don't mind a bit of law-breaking?

In 2007, Prince William's brother, Harry, was questioned by police after two hen harriers were shot on the Sandringham estate, an act witnessed from the neighbouring nature reserve. The bodies of the birds were never found, and because of this, a case was never brought.

Conservation organisations and grouse-shooting interests are now utterly at loggerheads. Grouse-shooters say it's time for compromise from conservationists. But it's not for conservationists to tell people that law-breaking is now acceptable.

Grouse-shooters are now very keen on "brood-management": ie, taking hen harrier chicks somewhere else. That's a non-starter until hen harriers are back on the moors and breeding reliably. And other less interventionist methods – such as diversionary feeding – should surely be tried first. Also, moving chicks requires concern for the lives of hen harriers: the grouse-shooting industry has something to prove here.

Some conservationists, including the Royal Society for the Protection of Birds – are exploring possibilities of licences for grouse-moors. More hardline elements advocate a ban on the entire industry. There is talk of bringing the Scottish law of vicarious liability into England: making a landowner legally responsible for his gamekeeper's crimes. There's scope for movement here.

But the first step has to come from the grouse-shooting industry: ie, a demonstrative willingness to abide by the the law. Their current modus operandi is sustained by breaking it. It's time the industry accepted that the tide is turning against this practice. It's also time the good and responsible people in shooting – and they exist – broke ranks and spoke out against colleagues who break the law.

I think that criminals are able to exploit weak and corrupt standards, so we must raise standards collectively....

And if Prince William wants people to listen to his good words about elephants and rhinos in Africa and Asia, it'd be a good thing if he also spoke out about birds of prey in Britain.