Where I live, I have access at my local feed store, to wild bird seed called Meaties. They are mostly hulled sunflower seeds. The chickens eat them enthusiastically. Personally, I wouldn't feed my chickens just black oil sunflower seeds in the shell because I think it's too much really rough, indigestible shell.
Lately my chickens have been enjoying the beginnings of fine spring weather and a dish of plain yogurt, a half of a Guinness chocolate cake (the cream cheese frosting was the first to go) and two cans of 2/$1.00 tuna fish.
They are bantams, they are enjoying being out of the coop, and the eggs they are finally laying couldn't be better!
I made a carrot cake this morning, and got a little too enthusiastic grating carrots, and I can tell you that my chickens were not the least bit interested in the extra carrots.