We have a few more nights below 20F so I forked out for the 15 pound bag of Sizzlin Heat seed mix. It does get a nice mix of birds in. I don't see much waste or shell mess at all. Another mix I had, has left cracked corn untouched.
White millet is ever popular and I look at these little fluffballs eating these very tiny seeds to survive. Boggles the mind.