As winter approaches, many of us will begin to feed the wild birds in our garden in earnest. I love seeing them in my garden. I have erected a small chicken wire frame underneath the feeders so the birds can feed in peace without my cat threatening them. This also means they can pick up dropped food safely from the ground. (If you want to make one, it's a round frame made of large aperture chicken wire which the birds can get through but not the cat. It also has a chicken wire lid. It is best weighted down to prevent it being tipped over, which my cat likes to try and do.)
At ALL times, wild birds should be discouraged from sharing poultry food and water. You can get special feeders which prevent wild birds and rats from accessing the feed e.g. Grandpa’s feeder. Feed garden birds in a different area of your garden and give them their own bird water. Keeping wild birds away from direct contact with your poultry helps keep your birds safe. In the migratory season it is particularly important you keep waterfowl away from your poultry due to the risk of Avian Influenza. Always contact your vet about unexplained deaths or large numbers of off-colour birds.
Wild birds can contract diseases from bird feeders and baths. As you clean your poultry feeders and drinkers regularly, so should you clean your wild bird feeders and bird baths too. This is particularly important around nesting and fledging time as the newly hatched chicks will be more susceptible to disease than their parents.
Be aware that different types of garden birds have different food preferences. The pigeons and your chickens (as a treat) may love the whole wheat inside cheap wild bird diets, but the smaller tits and finches are unlikely to eat these large pieces. "No-mess" bird seed is often more cost effective as the birds are likely to waste less of it and it will attract less slugs below your bird feeder.
See the RSPB website for more specific details.