Black overall; yellow eye. 32 cm (12.5 in) in length. In good light the male appears to have a purple iridescence, especially on the head and neck. The tail is wedge-shaped.
The breeding season begins in late March, peaks in April, and extends into early August. Breeding habitat is primarily conifer groves in residential or rural areas. Nesting is usually in loose colonies, with from 2-100 pairs breeding together. Nests are commonly in evergreen trees from 0.6-3.6 m (2-12 feet) above the ground, but occasionally the Common Grackle will also nest in cavities or on ledges. The cup-shaped nest is constructed from grass, twigs, other plant material, mud, and some paper, string, or other trash. The female lays 2-6 (usually 4-5) eggs that she incubates for 13-14 days. The young are altricial and fledge 16-20 days after hatching. The young are cared for by the adults while they are in the nest and for a few days after fledging.
In addition to habitat used for breeding, the Common Grackle inhabits crop lands, fields, and lawns during the winter. The diet of this species is quite variable. It includes insects, small vertebrates, bird eggs, nestlings, fruits, seeds, grains, nuts, and acorns. Most food is located by searching the ground and vegetation. During migration and winter, the Common Grackle flocks in very large groups with many other blackbird species; sometimes more than one million birds may roost together.
The Common Grackle occurs in most of the eastern United States all year. It spends only the breeding season in the Great Plains and in extreme northern portions of the United States and some of Canada. In the Southeast this species is abundant all year long.
The Common Grackle can become a nuisance when in large migratory and winter flocks. Because of the damage these flocks can cause to crops, they are sometimes controlled using scarecrows, noise repellents, and poisoned grain. This species is common throughout its southeastern range.
The two common species most similar to the Common Grackle are Brewer's Blackbird and the Boat-tailed Grackle. The Brewer's Blackbird is also all black with a purple iridescence, but it has a shorter tail and bill. The Boat-tailed Grackle is found in the coastal areas of the Southeast and East. It is larger than the Common Grackle, it has a longer tail, its iridescence is more blue, and its eyes are brown.