Sunflower seeds (unsalted of course) and pecans shelled. EWnglish walnuts shelled are great, too. The little ones make great pets if you get them before their eyes open. There was a Doctor who had his offices in his old family mansion down in Eufala, AL, IIRC. He had a squirrel that lived in the house, had its own room with a large tree branch for furnishings. The kids loved that entertainment. He would crawl all over people looking for treats in their pockets.
And pumpkin seeds and *almonds*.
The almonds are especially needful as they supply lots of calcium, magnesium, manganese and oodles of other vitamins and minerals.
Squiggy [the one I had to keep due to her birth defects] always got a serving of almonds every day no matter what else I fed her.