Black oil sunflower seeds (BOSS) in the shell are high nutrition treats. Corn is an all-time favorite of just about all animals (including humans) but is empty calories and almost zero nutrition. I give it to my birds occasionally, but prefer BOSS, fresh veggies and the like. Keep the peels from your carrots and cucumbers, old cucumbers, pumpkin with seeds, old grapes, dark leafy greens that you don't want to eat. All of those things are better than cracked corn. Corn is like giving them a cake. Be sparing with it. Oh, and giving "older" foods from the fridge is great, just not TOO old. Nothing rotting or rotten, and no salt, preservatives, MSG, etc. Keep it as organic as you can. Shelled sunflower seeds are great, but expensive. BOSS is cheaper and just as good.