What kind of bird is this and what does it eat?
Based on the photo, it looks like you have a fledgling American Goldfinch (Spinus tristis). Here's a photo of an adult female feeding a young goldfinch. This link has dietary information.



I would suggest contacting your local Wildlife Rehabilitation Centre or leaving the young guy where he was found. He could of jumped the nest a bit early, but typically the parents are always nearby.