We feed our finches only thistle seeds from a prepackaged bag. I buy it at Wal Mart.
We had to stop feeding the larger birds as the food was attracting raccoons, opossums and a groundhog. I don't like them in my yard. My two little dogs have a separate fenced in yard inside the bigger fence so they don't bother the dogs. They come into the yard before it gets dark. The wild animals leave big poop messes.