How many dead birds does it take to build a wind farm?

Nowhere is this more true than off the coast of Norfolk, where Ed Davey has just made one of those life and death decisions that come with the high office of Energy Secretary. Shockingly, he has decreed that guillotining 94 shaggy-crested terns a year is acceptable, even if you have no plans to put them in a sandwich.

There are limits, though, to that sort of behaviour - even in Norfolk. Which is why Davey has decided to block Centrica's plans to build the proposed 540MW Docking Shoal wind farm, whose tern-slicing blades might have powered 400,000 homes.

The logic? Nothing more than the Wash's "maximum mortality threshold", apparently. While halting Docking Shoal, Davey gave the go-ahead for another 580MW Centrica wind farm at Race Bank and a 560MW one, proposed by Warwick Energy, at Dudgeon. Costing £3bn between them, they're respectively, if not respectfully, on track to bump off 43 and 28 of the poor gull-like flappers a year.

Then there's the nearby Sheringham Shoal massacre site, already approved with its tern-liquidating quota of 13. Triton Knoll, also under consideration, is gearing up to do in nine a year.

Tot it all up and that's an annual "harvest", to quote from the department's release, of 93 - just one below Davey's limit, though already far too many for those ornithologists at the Joint Nature Conservation Committee and Natural England, who pleaded for a top whack of 75.

How the energy secretary arrived at his figure is a fine guide to the workings of modern Government. He commissioned a Population Viability Analysis, ruminating over such things as the "effects of kleptoparatism by black-headed gulls" on the local tern colony. Not to mention the problem of counting what actually constitutes a local tern, given their extraordinarily annoying habit of flying around a bit and inviting mates over from Denmark and the Netherlands for a spot of avian hanky-panky.

Still, it's good to see how seriously the Government is tackling Britain's energy needs, while attempting to meet those tricky renewable targets.

No-one likes on-shore windfarms, which spoil the view and are useless on puff-free days - but, unless you're a bird, it's much harder to object to the offshore variety.

Centrica had been working on its Docking Shoal plan since 2004, with the project awaiting planning consent for more than three and a half years.

In the process, it's run up a £10m bill, which works out as a fair bit per tern. Indeed, fitting them with NHS specs to spot what a wind turbine looks like could hardly have been pricier.

As for Davey, it's moments like these that demonstrate his aptitude for tough decisions. He might be a bit squeamish, though, for the defence department.