I don't give scratch during the summer because I've always heard it heats them up by being slow to digest or something along those lines. I give black oil sunflower seeds and fruit, like watermelon, strawberries, figs, or pears. Maybe I'm wrong, but that's how I do it.
I have been trying an approach that I think alleviates boredom like scratch, but it's basically just using vegetable scraps to make what I call chicken popsicles. Keeps them occupied for a good 1/2 hours pecking away and they get water.