My approach is not about the preservation of breeds, or production on a commercial scale but simply that birds are pets that give eggs.
I keep poultry, as did my parents and my grandparents. It's a good job too as if I had just read books about poultry keeping I'd never have taken it up. They make it all sound so complicated, and difficult. Especially those that insist you make the hen hut to their exact proportions, or that you must give your birds this or that in precise amounts. And when you get to the chapter on Pests and Diseases it puts you right off.
Fortunately I knew little of the 'proper' way, but had witnessed generations of keeping chickens. They need no more than the same common sense one applies to keeping a cat, dog or other pet. True, hens do scratch up the garden and they are not house trainable! But just compare a chicken's damage to that of a wandering sheep or goat and you are laughing. Having seen what those four footed fiends can do I strongly suggest no vegetarian quadruped is ever kept in or near any valued garden, not even a pet rabbit.
Of course you may regard poultry as stupid birds, however if you get to know them you'll find chickens are quite bright and geese are as intelligent as any dog. Indeed people pay far too much for a parrot when they could have a nice pullet for a few hundred pounds less! And while such exotic pets may require some expertise to manage backyard poultry is easy in comparison. Naturally if any animal looks unwell then a vet needs consulting but most fowls are so tough they rarely need any special doctoring until the day they drop. That is if they are living happily and not cooped up in some ghastly factory.
Chickens combine well with the productive garden where they fertilise, control pests and profitably consume much of the wastes, especially in an orchard where they eat the windfalls. For half of the year chickens can be run in the same cage as soft fruit but obviously need moving out before the fruits ripen. Hens are ideal moved in rotation on the vegetable area leaving it very well worked over and ready fertilised. A moveable hut and fence makes this work well where space is available, for small gardens though a permanent hut and fenced run is usually inevitable. Most hens are easily confined behind netting fences only a metre or so high, but some are escapologists and two metres is not enough, even if you clip their wings. Big breeds are much less trouble than bantams! I suggest Rhode Island Reds, Marans or Light Sussex.
If chickens have free run they find a lot of free food but if confined they need more feeding. A confined run also goes muddy so it is best kept strawed or covered in shredded newspaper to keep their feet dry. This then combines well with a pre-composting area. Everything from my garden weeding and tidying is spread out in their run for the hens to pick over first. Hens will gobble up brassica and salad leaves we wouldn't want, almost all seeds and bugs of any form are snacks especially ant eggs, many weeds are soon gone, they love fruits and even surplus root crops will be eaten if cooked first. After the hens have worked it over all the residues then go in the compost heap, ready inoculated with droppings.
Chickens are remarkably good survivors, they have had to be. Sadly this means they allow themselves to be badly treated and will still obligingly lay eggs. But their minimum requirements are surprisingly modest. They need food, fresh clean water, a nest box for laying and somewhere snug to perch offering night-time protection from the elements and major pests such as foxes. (Automatic pop hatches are available if you are lazy.)
Their food is easy, many buy a compounded feed, or a mixed grain. I prefer to give them organic mixed grain and extras. Of course the more hens you keep the more food you need to buy or grow. Their favourite seedy treats are sweet corn, sunflowers and Blessed thistle (Silybum marianum), pumpkins and marrows are also quickly munched. More strangely chickens are carnivores; a road killed rabbit is their tastiest fare. And you should have seen the cat's surprise when a chicken stole and ate the mouse she was playing with.
Most importantly hens eat all sorts of scraps we disdain and recycle high grade food items such as cheese rinds, bread crusts and fat trimmings into eggs. Far better that these food wastes are converted to eggs than merely composted, anyway you still get some lovely manure as a by product. A family of four probably wastes enough food to feed one or two chickens without buying any grain. And because chickens are so appealing, neighbour's or their children will bring scraps and garden surpluses to feed your flock - and they wouldn't bring you compost would they?
Feeding hens, checking their water and occasionally spring cleaning their accommodation is all the maintenance they need. They appreciate a clean dry run, this is difficult if it is small, and much easier if it is movable and part of the kitchen garden rotation. Straw or shredded newspaper spread regularly under their perches and in nest boxes will keep them, and their eggs, cleaner. They like to dust-bathe in wood ashes as this controls parasites, a tray can go in their hut. Supplying a little crushed oyster shell helps them make thick eggshells, but you can feed them back their own eggshells if you bake and crush them first, fed raw eggshell hens may get the habit and eat eggs!
You could buy a ready made hen hut but almost any dry place can be converted. Hens like to get up higher than the others so all perches should be level and as high as possible. Perches need to be rounded not square, and of wood, kept clean of parasites with an occasional coating of old frying oil. The same treatment will ease old birds scaly legs which is one of the few minor problems I've ever witnessed. Fleas and lice are prevented by wood ashing and derris dusting the litter in the nest boxes, these are traditionally orange crates but cardboard boxes do under cover.
Obviously egg production is the commonest reason for keeping poultry though some will want them for meat. Certainly if you allow them to hatch their own eggs you will get some cockerels which will become burdensome. I used to be a vegetarian but I now eat my surplus cockerels, I explain to them; they've had a good life though a short one and after all they might just have been a boiled egg. In fact unless you want to hatch eggs you do not need a cockerel as the hens lay anyway and they do not crow to annoy the neighbours.
Chickens are the favourite bird but ducks are even more garden, and people, friendly. They can be allowed free range in the vegetable garden as long as there is only a few of them, they do well in orchards and under soft fruit. A small pool is not essential but it would be cruel not to have one for them to swim in. They will destroy wildlife in ponds though. They do not however scratch and are more respectful of plants than chickens. Most usefully of all they love slugs and snails and spend most of their time dibbling their bills in under plants clearing the garden of pests. Duck eggs are just as good as hen for cooking and they lay more of them per year. Ducks eat much the same as hens but like to dibble in water for their grain.
Geese are very much bigger and eat mostly grass, they are ideal for larger gardens where they will maintain a good sward unaided and need little extra feeding. They extract clover, dandelions and buttercups from weedy turf and will stay behind low fences so can be used to maintain the paths in and around the vegetable beds. If they gain access though they will pinch carrots, destroy labels and eat out the roots of Jerusalem and Globe artichokes. Their eggs are enormous but make wonderful cakes and custards. Geese are also legendary watchdogs, ever alert they are often out all night, indeed except to lay eggs mine hardly ever go in their hut except in winter.
Poultry has a lot to offer the productive gardener, to say nothing of the interest they bring. On the down side they are a responsibility, but an easy one to cater for. And you'll find neighbours more willing to feed your birds than your potentially savage dog! And after all he doesn't lay such nice eggs!