Treats generally should be at 10% or less of their diet. An adult chicken eats about 1/4-1/3 pound per day (4-5 ounces). So, treats should be less than a tablespoon each....which isn’t much. That’s easy to think about for scratch, which can be measured in a spoon. But, the point being that the amount of treats given should be small -probably a lot smaller than many of us think!
my chickens are also in a run. I also give treats (scratch/veg/fruits), and they’ve also eaten the occasional baby bird that fell into their run

, but they are omnivores! i feed a 20% all-flock so that the protein doesn’t get diluted too low when they get treats. In the colder months, I rehydrate alfalfa pellets (sold for horses) and mix into wet feed as a treat. Alfalfa affects yolk color and alfalfa is 16% protein. I’ll toss in various greens, and handfuls of grass, but alwAys in the afternoon so they have already eaten a good amount of their feed. Sometimes they get A LOT of a treat...a whole Brussel sprout stalk, leaves and all, or a few watermelon rinds, etc, but I don’t do that every day. They love grapes, but cut them in half so it lessens The choking risk as they will fight over them and race. Blueberries and grapes and small tomatoes are great for exercising the girls and entertainment bc you can just throw one or a few out and they will race to get one.
you can add your general location to your profile, but if you are somewhere hot, then a “treat” in the warm months will be lots of fresh water that is cool, and you can add a few pans or similar of shallow water with ice blocks for them to cool off in...they will stand in the cool water and drink.
enjoy your chicks!!