"Chickens are flightless birds and they feel vulnerable from above," says Widdowson. "Before, even a crow flying over was enough to send them running for cover. And they were originally jungle fowl, used to a canopy of leaves overhead. Since the trees were planted, my chickens spend much more time outside and range much further. Other farmers have taken up the idea, too."
Widdowson's eggs, marketed under the Woodland Egg brand, are sold in Sainsbury's. He is a model free-range egg-farmer, and this is hen heaven compared to the other end of the production scale: the battery cage.
There can be no doubt that most British consumers don't want to buy battery eggs. A survey carried out by Mori for the RSPCA this year shows that 85 per cent of consumers believe battery cages should be banned. And yet, around two-thirds of the eggs produced in this country still come from battery farming. Although many of us seek out free-range eggs in their shells, a huge proportion of pre-prepared foods, including cakes, mayonnaise and quiches, are made with battery eggs. At the bottom end of the market, liquid or powdered egg, imported from countries such as Thailand or India, is used.
But free range production is growing. Ten years ago, less than 15 per cent of British eggs were produced in barn or free-range systems; by 2004, the share had risen to 34 per cent. The latest figures, out last month, show that the value of free-range egg sales has now overtaken cage-produced eggs: free range and organic eggs accounted for more than 47 per cent of the value of the egg market for the year to September, with caged eggs at just under 46 per cent.
This is largely due to consumer pressure. "People have become far more aware of how we farm and how the battery hen leads a very restricted life - you have to question what the life of that hen is like," says Widdowson. "Retailers such as Marks & Spencer and Waitrose, who have introduced a policy of only using free-range eggs in their food ranges, have been brilliant, as has McDonald's, which also only uses free-range eggs."
But this poses a problem for free-range farmers: meeting demand while maintaining standards. The essence of free range is providing as natural a life as possible for the birds, but chickens can be kept in large production units while still, technically, having free-range status. Although any free-range system is infinitely better than battery farming, chickens do not naturally live in large flocks, and in practice it is often only the most assertive birds that will go out to forage and dust-bath. And free-range hens are still de-beaked to prevent the aggressive behaviour that stems from living in large flocks.
Also, farmers are coming under pressure from supermarkets to bring prices down. "The only way to do that is to intensify production," says Widdowson. "We need to be very careful because the pressure is definitely on to produce cheaper free-range eggs. We need to retain consumer confidence and fight very hard to ensure the industry does all it can to keep standards high. The balance between affordable free-range eggs and hen welfare is a knife-edge: if we lose consumer confidence, we've lost everything."
The possible introduction of multi-tiered hen houses is controversial. Multi-tiering doesn't approach battery density, but it allows chickens to be housed in layered accommodation, with EU regulations allowing up to three tiers. "It is the main system on the Continent and there are some huge set-ups over there with an awful lot of birds in one house," says Widdowson. "Some aspects are good - chickens like using overhead space to flap around in and there is a belt system to remove droppings. An enthusiastic free-range farmer could use the multi-tiered system perfectly well, but multi-tiering wants watching and is causing some concern. Some of the excesses of the continental system wouldn't work here. Consumers wouldn't think this is how chickens should be kept."
The EU voted in 1999 to phase out battery cages by 2012, and, in general, European law has driven down stock densities. This, says Philip Lymbery, the chief executive of Compassion in World Farming, which campaigns for higher standards of animal welfare, is down to consumer insistence across the Continent. But even this legislation, he warns, is not set in stone. "Unfortunately, the food system in the EU is geared towards driving down costs, and our food systems are geared towards getting food as cheaply as possible," he points out. "Phasing out the battery cage is not necessarily a done deal. The original legislation had a built-in review date and that review is under way now - a decision will be reached over the next 12 months. It is my belief that the egg industry is actively trying to undermine the laying-hens directive, and there is a chance that the EU will pull back unless we, as citizens, make our feelings very clear."
Although the battery cage will go eventually, it won't happen for some years yet. Meanwhile, Jane Howorth, who runs the Battery Hen Welfare Trust (BHWT) from her home in Devon, remains a committed champion of the chickens she calls the "underdogs of the animal world". Howorth is no balaclava-clad animal lib activist. Instead, she goes in via the front door. She calls local farmers and asks if she can take away chickens they have no further use for. Many are glad to see the birds go to good homes. Farmers, says Howorth, are not to blame for the battery-egg industry - they operate legally and respond to demand. "It's up to politicians when it comes to the law, and consumers to be discerning when they buy," she says.
Although the hens Howorth saves are only a tiny proportion of the total UK battery population of more than 20 million, she feels it is worthwhile. "It's so rewarding seeing a bird that was so bald she looked ready for the oven to start to scratch and peck. Their feathers grow back surprisingly quickly."
A free-range hen can live to eight or nine years, but a battery bird is considered past her peak aged one, although she can lay productively for years more. My half-dozen rehabilitated battery hens are proof that it takes only a few weeks for pallid yolks to become proud, orange domes.
Howorth set up the BHWT two years ago and was worried at first that no one would come forward to take on the first group of 100 scruffy, featherless birds. But word has spread, and now she can rehome hundreds at a time.
Avian flu is a threat to the UK free-range egg industry. "At the moment, all our birds are still outside and Defra [Department for Environment, Food and Rural Affairs] has described the risk to the UK poultry flock as low," says Widdowson. "If we do have to bring our birds inside, we've got problems. We can make them comfortable indoors, though they won't be very happy, and in the short term we can still call the eggs free range, but in the long term, how will the market stand it? And my big worry is the exit strategy: if the hens go inside, how do we decide when they can be brought out again?"
If the flu risk escalates, hundreds of thousands of birds could be brought indoors. Then, says Howorth, free-range egg farmers will need backing more than ever. "Bird flu has been spread from birds kept abroad in the worst intensively farmed conditions. We should support our own farmers, who are striving to create a more natural system."
Battery Hen Welfare Trust (07773 596 927; www.thehenshouse.co.uk)
What you're buying
Caged-hen eggs (59.9 per cent of British eggs, according to the researchers Taylor Nelson Sofres). This basically means battery hens that are kept in small cages all their short lives, unable to perch, scratch, preen or move around. They enter the cages as chicks and are "cleared out" after a year to be slaughtered and then either processed into food products or dumped in landfill sites.
Barn eggs (5.8 per cent). Hens are kept indoors but have more space to express their natural behaviour, and perch space of 15cm per hen is stipulated.
Free-range eggs (30.9 per cent). Chickens have outside access, and flock sizes are regulated; no more than 1,000 birds can be kept per acre. RSPCA freedom food assurances and Lion standards allow no more than 400 chickens per acre.
Organic free-range eggs (3.3 per cent). The birds are kept in small units, in small flocks - this is the closest to the image most people would have of free-range.