What are all birds foods they can eat?
Birds eat all food sources, though individual birds do not use all the foods available. Some, such as crows and Blue jays, are generalists able to use a variety of foods, birds like eagles eat only meat, warblers only insects, and cardinals only seeds. Birds can eat seeds, insects, nectar, meat, berries, and plant material, depending on their physical adaptations to do so.
There are lots of human foods you can feed wild birds, such as bread crumbs, sunflower seeds, chopped nuts and fruits (such as apples and pears), and raisins. I even have all types of birds that fly down to my dog's food bowl on the patio and eat the dry dog food, but the kinds with smaller pieces are much easier for them to eat. Anything that is raw and unprocessed is OK.
Birds will eat whatever they become accustomed to eating and what they like. You can try offering cucumber if you want. Be aware that birds will not readily eat foods they don't recognize as being food, so you have to keep offering new foods every day until the bird realizes that this new item is food and tries it!