Common Grackles are large, noisy, and gregarious birds that often flock with other blackbirds, cowbirds, and starlings, especially in winter. At feeders they tower over other birds and push them aside to get at food. Grackles typically forage on the ground and roost high in trees or on power lines.
Common Grackles sometimes nest in loose colonies of up to 200 pairs, showing little territoriality except in the immediate area of the nest. Common Grackles eat mostly seeds, particularly agricultural grains such as corn and rice. Other seeds include sunflower seeds, acorns, and tree seeds. In summer, one-quarter or more of a grackle’s diet may be animals, including beetles, grasshoppers, caterpillars, spiders, crustaceans, mollusks, fish, frogs, salamanders, mice, and other birds.
Common Grackles do well in human landscapes, using scattered trees for nesting and open ground for foraging. Typical natural habitats include open woodland, forest edge, grassland, meadows, swamps, marshes, and palmetto hammocks. Unbroken tracts of forest are the only places where you are unlikely to find Common Grackles.
Those raggedy figures out in cornfields may be called scare-crows, but grackles are the #1 threat to corn. They eat ripening corn as well as corn sprouts, and their habit of foraging in big flocks means they have a multimillion dollar impact. Some people have tried to reduce their effects by spraying a foul-tasting chemical on corn sprouts or by culling grackles at their roosts.
Common Grackles are resourceful foragers. They sometimes follow plows to catch invertebrates and mice, wade into water to catch small fish, pick leeches off the legs of turtles, steal worms from American Robins, raid nests, and kill and eat adult birds.
Grackles have a hard keel on the inside of the upper mandible that they use for sawing open acorns. Typically they score the outside of the narrow end, then bite the acorn open.
In winter, Common Grackles forage and roost in large communal flocks with several different species of blackbird. Sometimes these flocks can number in the millions of individuals.
The oldest recorded Common Grackle was a male, and at least 23 years old when he was killed by a raptor in Minnesota.
