The main diet of Wild Finches comprises of: dry and fresh thistle, garden seeds of hollyhock, dandelions, zinnia, coreopsis, lettuce and Swiss chard. The bird's food should be placed away from other bird's feeders at all times.
1 Additional Answer
What do wild finches eat? The wild finch, of which there are many kinds like thistle, seeds, fruit and suet. They will eat from hopper feeders, tube feeders and sock feeders. You can find more information here: http://birdwatchin.com/