The Common Grackle Quiscalus quiscula is a large icterid which is found in great numbers through much of North America.
Adult Common Grackles measure from 11 to 13 inches in length. Common Grackles are less sexually dimorphic than larger grackle species but the differences between the sexes can still be noticeable. Adults have a long, dark bill, pale yellowish eyes and a long tail; its feathers appear black with purple, green or blue iridescence on the head, and primarily bronze sheen in the body plumage. The adult female, beyond being smaller, is usually less iridescent; her tail in particular is shorter, and unlike the males, does not keel in flight and is brown with no purple or blue gloss. The juvenile is brown with dark brown eyes.
The Common Grackle forages on the ground, in shallow water or in shrubs; it will steal food from other birds. It is omnivorous, eating insects, minnows, frogs, eggs, berries, seeds, grain and even small birds and mice. Grackles at outdoor eating areas often wait eagerly until someone drops some food. They will rush forward and try to grab it, often snatching food out of the beak of another bird. Grackles prefer to eat from the ground at birdfeeders, making scattered seed an excellent choice of food for them. In shopping centers, grackles can be regularly seen foraging for bugs, especially after a lawn trimming.
Along with some other species of grackles, the Common Grackle is known to practice "anting," rubbing insects on its feathers to apply liquids such as formic acid secreted by the insects.
The grackle can mimic the sounds of other birds or even humans, though not as precisely as the mockingbird, which is known to share its habitat in the Southeastern United States.
In the breeding season, males tip their heads back and fluff up feathers to display and keep other males away. This same behavior is used as a defensive posture to attempt to intimidate predators. Male Common Grackles are less aggressive toward one another, and more cooperative and social, than the larger boat-tailed grackle species.
Grackles tend to congregate in large groups, popularly referred to as a plague or annoyance. This enables them to detect birds invading their territory, and predators, which are mobbed en masse to deter the intruders.
Despite a currently robust population, a recent study by the National Audubon Society of data from the Christmas Bird Count indicated that populations had declined by 61% to a population of 73 million from historic highs of over 190 million birds.
Unlike many birds, the grackle benefits from the expansion of human populations due to its resourceful and opportunistic nature. Common Grackles are considered a serious threat to crops by some, and notoriously difficult to exterminate and usually require the use of hawks or similar large birds of prey.