Find out more about what this bird likes to eat and what feeder is best by using the Project FeederWatch The "western" great-tailed grackles, from nelsoni in the north, to coastal forms in west Mexico south to Guerrero, are small. During spring and fall migration and winter, common grackles eat mostly grains … Great-tailed Grackles eat plant material year round, including grains such as corn, sorghum, and oats as well as fruits. Great-tailed grackles are noted for their diverse foraging habits. In summer and early fall, animals make up half or more of their diet, with females eating up to 80% animal matter. Cracked corn and milo are particular favorites. During breeding season, their diets consist mainly of insects. Prey includes grasshoppers, beetles, spiders, bees, … Great-tailed Grackles will take seed spread beneath feeders, often chasing off smaller birds. They are also known to eat other birds' eggs and nestlings, and occasionally kill and eat other adult birds, particularly adult House Sparrows. They turn over objects to search for food underneath, including crustaceans, insects, and worms, they hunt tadpoles and fish by wading into shallow water, and although they do not swim, they catch fish by flying … They extract larvae and insects from grassy areas; eat lizards, nestlings, and eggs; forage in freshly plowed land; remove parasites from cattle, and eat fruits (e.g., bananas, berries) and grains (e.g., maize, corn on the cob by opening the husks). Common Grackles forage primarily on the ground. However the birds are opportunistic and can eat fish, small frogs, salamanders, mice, and small bats.