As the autumn approaches the northern hemisphere the weather gets colder. Local bird populations are looking for food. Some of them need to stock up so they can migrate others so they can overwinter in the UK.
You can get bird foods from local shops and pet stores. Grain, peanuts, sunflower seeds, fat balls, together with a fresh supply of water is what they need. If you feed them bread make sure it has been soaked in water, otherwise it can swell up in their crops and cause harm to them.
See your local nature charities for more information about feeding specific birds.