When my mother was a young girl, she – like most families in the country – kept a few chickens in the back yard. Once a day she went out and gave them household scraps, and they rushed over to greet her, flapping their wings, and she would return a few kind words to them. Every morning she collected the fresh eggs from their small shed, which gave them somewhere warm and safe to perch at night and lay their eggs.

Eggs like these were vital in wartime Britain; highly valued for the protein that they provided for the family. In between my mother’s visits, the hens scratched around the yard for insects and seeds, dustbathed in the earth to keep themselves clean and rested under the hedge in the warm sunshine.

Nowadays the eggs that you eat will probably have been produced in large factories, each containing many thousands of birds.

An entire industry has emerged in the space of just over 50 years. This started in the most war-affected countries of Europe, where the risk to food security that occurred in World War 2 had been so great that it led to governments developing “factory farms”. Here, large numbers of animals were kept in a small space and fed on pelleted food brought in from another type of factory, the feed mill.

Chickens were better suited to this process than cattle or sheep, and two types of factories emerged: one for birds that were kept to produce eggs and another for those used for meat.

Agricultural scientists developed new egg-producing strains of chicken which produced an egg almost every day of the year. In the meat strains, the researchers selected for rapid growth, particularly of breast muscle (when taken to excess, this has caused heart and leg problems and increased mortality). Birds now grow to their market weight in just 35 days: their lives are short.

Recently while I was driving along the Great Western Highway in New South Wales, I passed the largest egg production facility in the Southern Hemisphere. It houses 2 million birds and employs 500 people to manage them. The operations include a number of methods of producing eggs, to meet the needs of those consumers who think that when birds have more space their welfare is improved.

There are three main options for the large scale egg producers. The first is barns with rows and rows of cages containing five birds each, which provides about an A4 piece of paper of space per bird.

There are two main problems with this system: the restricted space stops them performing their natural behaviours such as flapping their wings. And the barrenness of the cage provides no possibility to dust bathe or forage in the dirt. The chickens' food is provided automatically by a conveyor belt and their dung is removed equally automatically by another belt, so the bird is just a machine in the middle of the process.

The second option is to have groups of several thousand birds loose in barns. Consumers pay a premium for these type of eggs. This set-up improves the birds’ behavioural freedom because there is more space and variety in the environment, but there is increased fighting and even cannibalism.

This is because chickens are territorial animals with a strict hierarchy, and in such large groups they constantly meet birds that they don’t recognise.

A third alternative is allowing birds to have access to both a house and free range. This gives them the opportunity to go outside, but usually offers little protection from aerial predators or the extremes of weather. As a result the birds often don’t venture outside.

So which eggs should you buy, when presented with a bewildering choice in the supermarkets? We instinctively believe that more space is better for the birds. But space may not be as important as a small group size to the birds. Our anthropomorphic assessment may be wrong from a bird’s eye.

In the tropical jungle where they evolved, chickens existed in groups of 10-15 birds with lots of space. How can we provide both space and a small group size in an economic system of production?

When I lived in the country I kept a few chickens, about a dozen layers. They shared a field with some horses and had access to a garden shed at night, fitted with a raised bar for them to roost on at night (mimicking the tree branches in the jungle), and nest boxes in which they laid their eggs.

The excellent welfare of these birds was borne out by their long lives and wide range of behaviours. And the eggs tasted much better than those from the supermarkets! So maybe the best way to support chicken welfare is to hunt down that backyard producer that sells a few eggs on the side. Even better, if you have a yard buy a few chooks and recycle your vegetable scraps.

In conventional meat chicken systems, birds are kept on the floor of a large barn, usually at more than 20 birds per m². This limits both locomotion and environmental exploration, and the birds spend longer just sleeping and congregating around the feeders. Birds become fearful as they cannot recognise other birds in the large flocks, and their contact with acidic excreta causes dermatitis.

Organic chickens – according to the international NASAA standard – are provided least eight hours continuous darkness every 24 hours, and must have access to natural light and forage areas for at least six hours per day. Farmers have to provide at least one square meter for every five birds.

Nowadays in Australia almost everyone can eat chicken meat every day if they wish, such is the affordability of factory-produced meat. When my mother was growing up it was a rare treat. Now its low cost encourages us to eat more than we need.

We have substituted vegetables in our diet with chicken products of very high nutritive value and this means we have surplus nutrients to store. Fast food outlets offering chicken meat at a fraction of the cost of pre-factory farming chickens must take some of the blame for the current obesity epidemic.

We can all help to reduce chicken welfare problems by not eating factory-farmed birds.

But in many parts of the world decisions on buying chicken meat or eggs are not influenced by the welfare of the birds. Developing countries – especially China, Brazil, Indonesia and Thailand – have copied the Western factory farming model and are now leading the world in chicken meat production.

These countries have no effective legislation governing poultry welfare, they don’t contribute to research to improve welfare, and perhaps most importantly they have been cutting down rainforest to grow the soya and cereals necessary to feed the birds. Economic growth in the developing countries is producing an increased demand for chicken meat, and consideration for the birds’ welfare is a luxury reserved for the wealthiest countries, in Europe, North America and Australia.

The emerging middle class in many developing nations seems guaranteed to increase demand for factory-produced poultry products, despite their questionability on animal welfare and environmental grounds. The main hope lies in agreeing effective international legislation to control this inefficient and unethical way of feeding people.