Adult females, beyond being smaller, are usually less iridescent; their tails in particular are shorter, and unlike the males, do not keel (display a longitudinal ridge) in flight and are brown with no purple or blue gloss.

The distribution of the common grackle is largely explained by annual mean temperature, and the species has expanded its range by greater than three-fold since the last glacial maximum, approximately 22,000 years ago.

It is omnivorous, eating insects, minnows, frogs, eggs, berries, seeds, grain, and even small birds and rodents.

Grackles prefer to eat from the ground at bird feeders, making scattered seed an excellent choice of food for them.

The grackle can also 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.

Unlike many birds, the common grackle benefits from the expansion of human populations due to its resourceful and opportunistic nature.

Common grackles are considered to be a serious threat to crops by some, and are notoriously difficult to control; this usually requires the use of hawks or similar large birds of prey.

[13] Though the exact mechanism is poorly understood, several studies have examined the ability of the common grackle to interpret the Earth's magnetic field—or in this case, the variability of it.

The common grackle (like most of its Quiscalus relatives) has been found to be attuned to a dynamic magnetic field to a scientifically significant degree.