During autumn, robins have so much natural food available that they don't need any supplements anyway. But robins overwintering in northern states and provinces are probably going to become more and more common. During winter, these birds really will benefit from feeders. The two things robins DO like are fruit and invertebrates, such as worms and insects. If robins happen to overwinter near you, you can offer them frozen or fresh fruit.
Favorites are apple slices, raisins, blueberries, strawberries, raspberries, and cherries.
Or you can offer them fresh insects. Not to worry. Mealworms are the best choice, and they're easy to find. You can buy them at pet stores or through the World Wide Web. Grubco The problem is that it's hard to get robins to notice frozen mealworms.