Chicken foraging system

In an ideal world my chickens and ducks would happily free range in a large sunny pasture with some tree cover, eating insects and wild plants and topping up with some shop bought pellets. If that wasn't possible I'd have them in large runs that I could rotate, ensuring they were always on fresh grass.
Sadly, that's not possible in my garden. It's a decent size but we also have to fit in all the things the rest of the family deem essential and as it's in between two other gardens with mature hedges pretty much impossible to chicken-proof.
So, I've given them the largest area I can (the chickens, bantams and ducks are all in together) and have incorporated trees for shade. The trees also provide some food- the plum trees in particular provide plenty of windfalls in the autumn.

Barbara the bantam in the shade and scratching through twigs and dry leaves

I want to increase the amount of food the birds can find for themselves. Chicken pellets are expensive and, although I buy organic or at least GM free from a local family-run business and they come in paper sacks, are highly processed. I also avoid soya, a cheap source of protein in animal feed that we can't grow in the UK and so has to be be imported and, again, highly processed before feeding. I'm also pretty sure the chickens and ducks would prefer to eat a variety of foods rather than a monotonous diet of layers pellets just as much as I would prefer not to have to buy sacks of food. I also think the eggs must be more nutritious if the birds are eating a wide range of foods rather than the macro-nutrients in commercial feed. You can certainly tell the difference in the colour of the yolks when they've been eating lots of greens. A closed loop system with minimal external feeding is also more sustainable as well as frugal.

I collect weeds when I'm out walking the dog, especially dandelions and goosegrass in Spring, and they get plants from around the garden (they're fans of borage which is very useful as it self-seeds freely) but I've rather have foods that they can find for themselves.

Borage

Research mostly brought up posts from sub-tropical areas with plants that I can't grow here. I did find this article  which debates the difference between a chicken foraging and chicken scavenging system. Essentially, he defines foraging as a system planned for the chickens whereas a scavenging system is planned for human consumption with the chickens getting leftovers. I think what I need is somewhere between the two. The plums are for us, but they can eat the windfalls (which also keeps wasp numbers down as they eat them before they become wasp magnets). There are raspberry canes growing in the tree in their run (inherited from the previous owners) and we pick some but the chickens and ducks get those they can reach or those that drop. I also give them any that have gone over or that are very damaged as I pick. I can do this in the UK but am not allowed to bring food into the kitchen and then feed them the scraps according to DEFRA regulations designed to prevent the spread of diseases like Foot and Mouth by possible contamination by meat.

Raspberry canes growing in a small tree

So, more online research and Sustainable Smallholding has again been the best source of information. Providing insect habitats for the chickens to forage in is a big part of the answer. I've always had a pile of rotting tree stumps in their run but I've added another couple of piles to turn regularly, exposing worms, slugs, woodlice and other invertebrates for them. The woodlice are the most popular and I think probably give them a bigger protein hit than the worms but I keep encouraging slug munching and I throw them any I find in the vegetable garden. (do try to leave the slugs in the 'forest garden' for wildlife and the plants in there are less susceptible to slug damage anyway.)
Leaf litter I hadn't thought about, but the trees providing shade will also provide a fresh layer of leaf litter every autumn and after reading the article I have added some bamboo I dug up from another part of the border where it had come in under the fence from a neighbour. I think the chickens scratching will stop it from getting too rampant and if not it will be easy enough to monitor and hey- bamboo shoots!

Duck shed with a transplanted bamboo in the foreground next to a log pile and new Buddleja Globosa in the chicken wire

I've added a buddleia I got from a plant sale to attract more insects and have taken cuttings to add another. I'll also split my yarrow plant to attract more insects and take currant cuttings to add fruit. Plants are protected with chicken wire until they get established and/or tall enough to tolerate some leaf eating.
To add to diversity and leaf dropping I've planted a climbing rose I was given from a friend's garden and a golden hop against the duck shed.
Leycesteria Formosa is also known as Pheasant berry because they love it's berries and apparently so do chickens and it's also attractive to insects so I'm looking out for one of those to add.
Finally, I have some wooden frames covered with chicken wire to allow the chickens to peck at plants without entirely decimating them. They look a bit sad at the moment because of the heat but I have sown some wild grass seed and will add perpetual spinach and other tasty additions for them.

Qaratsetseg posing on the wire covered frame

When I extended the run I left most of a hemerocallis (daylily) because it was too hard to dig out. They eat the flowers (so do I, so I'm pampering the part I moved)  and Sylvia the duck especially enjoys sitting under the drooping leaves so I'm glad I did.

Mollie and Blueberry in between the hemerocallis

I did plan sunflowers but it was an old packet and they didn't germinate. It's on next year's list. I'm tempted to sow a small patch of wheat or barley too. If I do it in their run they can peck through the stalks once they've eaten the grains.