These omnivorous birds seek out earthworms, spiders, caterpillars, snails, and grasshoppers, and so by letting your garden go untended or setting out a container with mealworms, you could attract these creatures. Fruits also make up about 60% of a robin’s diet, so fruit-bearing trees or bushes, a plate of fruit, jelly, or suet cakes will make your garden irresistible to robins.