American Goldfinches

I get a lot of goldfinches at my feeders and yard in the winter and spring. Then come summer, they are only rarely seen. In winter they are a drab olive yellow color, but in the summer they turn the most brilliant shade of bright yellow. They love thistle seed and have a very musical song. At times I have seen as many as ten of these guys on the thistle feeders.
They especially seem to like the thistle sock I recently put up. They also will eat black oil sunflower seeds.