Wild birdseed is expensive compared to scratch grain. You can get scratch grain (4 or 5 grains) for $13 here for 50 pounds. Wild bird seed is probably more than triple that cost.
Though my chicks LOVE millet. I haven't bought wild bird feed since I expanded to so many :P
:)
BOSS (black oil sunflower seeds) is better than corn, and they do love it!
Right now I use a 3 grain scratch. Corn, barley and oats I believe. It seems to have less corn than the other two grains. The chickens love it. I toss it out every morning - but only one scoop for 150 birds.
Don't put it in a feeder. Only offer sparingly.
They are better off with you tossing them lettuce to be honest :) Get some of the 50% lettuce at the grocery store if you can't get any locally.