I also discovered something very interesting about Painted Buntings, which may explain why I haven't gotten them at the bird feeders before. Most of the cheaper bird seed mixes have a lot of millet and milo in them, with only a few sunflower seeds mixed in. Years ago I noticed most birds just pick the sunflower seeds out and scatter the rest on the ground, so I started buying only pure black oil sunflower seeds. It's more expensive, but none is wasted. Everybody seemed to like it: chickadees, titmice, cardinals, doves, house finches, everybody.
As you can see from the pictures, this seems to be the preferred food for the buntings! The house finches, chickadees, and titmice all stick to the sunflower seeds, but the buntings go to the other feeder with the seed mix. Also, if I look closely enough, it looks like they are actually picking the small seeds out and discarding the sunflower seeds in the mix.
After doing some research, I think it's probably the millet they like the best. That's the smallest seed in the mix. Milo is a larger, reddish-colored seed, and according to the Cornell Ornithology website, hardly any birds like that stuff. Maybe once I run out of this seed mix, I'll buy some millet by itself just for the buntings.