They are seed eaters. I know they like thistle seeds but they seem pretty happy eating the black oil sunflower seeds that we provide all year round. Sometimes we have several goldfinch families vying for seed on the feeders. They are sociable birds and gather in groups. They hang out with the house finches, too.
Goldfinches build nests a little later than most birds because that’s when the seeds ripen. We discovered a nest about five feet off the ground, tucked into the branches of our forsythia bush. We kept a respectful distance until the nest was empty but then it was a welcome reminder all through the snowy winter that no matter the weather spring, and nests, will come again.
The male goldfinch is easy to spot if you want to interest kids in bird watching. Here is a free printable coloring page for the kids: http://www.friendsacrossamerica.com/colorstatenjbirdflower.html