Up in the aidrondacks they go crazy over young turnip shoots. Never done it, but could easily shoot several with a 22. Last time I was up there I was 4 for 4. Walking into each food plot and bumping into a few each time. Millet would be good. I would also put one or two spots of small pebbles around for their crops.
You would need a seed head that holds into the winter for them really. You might be onto something wth sorghum or millet. I have never used either. When I hunted grouse up there, I'd see my dog excited but coudn't figure out why until I looked up. Birch trees catkins.
Looking into a few bird crabapple trees to provide the critters with winters.
NYSDEC has a grouse packet. for their spring seedling sale.
American hazelnut, red osier dogwood, pussy willow, white spruce, witch hazel,
winged sumac
My old hunting club grew wheat for their pheasant releases. I tend to think that would be a bit better than rye or oats far a the big 3 go.