Gamekeepers have been catching wild birds in traps and leaving them in distress for up to two days, to prop up the game-bird shooting industry.

Undercover footage taken on a game farm and obtained by The Independent, reveals how crows were confined in “cruel” cages – with one left without water for more than 24 hours.

Campaigners said the scenes were a typical example of the unseen “dirty secret” of game-bird shooting, a situation they described as the “secret carnage of native wildlife” across the UK.

The speeded up footage, taken on a Somerset farm over nearly 48 hours, shows a crow trapped in one side of a cage called a Larsen trap, a type commonly, and legally, used by the shooting industry to catch crows and magpies, which are blamed for preying on birds reared for the shooting season.

Larsen traps, available online, usually contain one bird in a compartment. Their distressed cries attract other birds into a separate compartment.

The birds are then killed by a gamekeeper to reduce their numbers and protect pheasants.

The footage was taken at Bonson Wood Game Farm in Somerset, where two traps were set side by side – one with a single decoy bird and the other with three birds crammed into the decoy compartment.

Even when the legal requirements are met, life is simply hellish for the birds Fiona Pereira

By law, the traps should be checked “at least once every day, at intervals of no more than 24 hours”.

However, the film shot by the Animal Aid rights organisation shows the trap was not inspected for almost 35 hours. At one point, a tractor went past but the driver did not get out to look at the birds.

“This was especially concerning, because during this time one of the decoy birds had kicked over a small and totally unsuitable water dish in his cage,” said Fiona Pereira, campaign manager at Animal Aid. “Our film showed that he was without water for more than 24 hours.”

The filming took place at the end of June, during the heatwave, when temperatures hit 28C.

Animal Aid, which reported its findings to police and is waiting to hear back, released the footage a week before the start of the pheasant-shooting season, on 1 October.

The film was published a day after a decision to end pheasant shooting on public land in Wales.

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Natural Resources Wales (NRW) said it would not be renewing leases to shoot game birds from March next year, and it would also not support the breeding of pheasants on government-owned estates. The Welsh government had strongly opposed the leases.

Ms Pereira said the three birds together had suffered feather loss injuries, and were prone to getting their wings caught on a cage perch as they tried to avoid one another.

“We also observed the distressed birds flying at the sides of the cages to try to escape,” she said.

The camera stopped filming after 48 hours, so it is not known how much longer the crows were confined.

“What is clear, however, is that the birds were stressed and desperate to be released,” said Ms Pereira. “The poor bird who was left without water must have suffered greatly. Larsens and other traps are one of the shooting industry’s dirty secrets. Confining highly intelligent birds in a small space for days at a time causes them enormous stress, and even physical injuries.

“Most people don’t realise that these traps are all over the countryside. Even when the legal requirements are met, life is simply hellish for the birds because no bird wants to be caged. It must be terrifying for the birds trapped as night fell, because there would have been foxes that prey on crows roaming around.

“To cage birds that want to fly freely is abhorrently cruel when you think about what it means. These traps are in common use by an industry that breeds game birds only to shoot them out of the sky for ‘sport’, so it’s little wonder they treat wildlife with the same cruelty meted out to the feathered targets they breed.”

It is estimated between 35 million and 50 million pheasants and partridges are bred for shooting each year, with shooters each paying up to £1,000 to kill up to 400 birds per day.

Bonson Wood game farm questioned the accuracy of the video.

Nicholas Pardoe, who runs the farm and is chairman of the Game Farmers Association, said: “The farm is private property and the video was made without permission, which is an offence, and as such would not be able to stand as evidence in a court of law. Whilst there is a clock in the corner of the screen, there is no way of knowing it is set accurately or that it indeed shows the correct passage of time. The video is heavily edited and does not amount to proof of any offence.

“There is clear intent that the bird should have water, evidenced by the presence of a water bowl. No bird was shown to die or even to have become weak. The filmmaker clearly has an agenda, which is to stop the use of Larsen traps. The video was taken some time ago, and this is the first I have heard of it.

“If they really had animal welfare concerns, they should have raised them with me or a member of my staff at the time, or even reported it to the relevant authorities, rather than releasing a film a few months later.”