Indigo buntings are small songbirds, roughly about the size of a sparrow. Males in their breeding plumage have a brilliant jewel-like coloring that makes them a favorite among birdwatchers. Vibrant shades of blue cover their bodies, with slightly darker blues on their head. Wingtips and tails are blackish. Females, however, are mostly brown with white undersides and faint brown streaks on the breast. Males lose their breeding color during the fall and take on the brown coloration of females. Both sexes have short, cone-shaped beaks and dark gray legs.

Adults are 4.5-5.9 inches (11.5-15 centimeters) long and weigh about half an ounce (14.5 grams). Males are a little larger than females.

Indigo buntings live in fields, pastures, rural areas and edges of woodlands. 

In the winter, these birds can be found throughout the Caribbean, Central America, and northern South America. In the spring, they migrate northward traveling across the Gulf of Mexico to the Eastern and Midwestern United States as well as southeastern Canada.

Average lifespan is two to three years, but some individuals can live up to 10 years.

Males sing a cheerful, double-noted sweet-sweet chew-chew song to mark their territory and attract females during the breeding season. 

Indigo buntings eat insects, seeds, and berries.

These birds are active during the day and sleep at night.

During the breeding season, males defend their territory from other males.

In spring males stake out their territory through song, which they learn from other males and sometimes other species of birds. After pairing up, females build a cup-shaped nest out of plant material in dense shrubs or low trees. Females lay a clutch of one to four white to bluish-white eggs, which they incubate for about two weeks.

Care for the nestlings is mostly done by females, although sometimes the male will take over feeding duties when the young are ready to fledge, or if the female moves on to start another nest. Nourished by a steady diet of insects caught by their parents, most young indigo buntings are ready to leave the nest nine to twelve days after hatching.

Increased urbanization, intensive agriculture, frequent mowing of roadsides and fields, and deforestation all contribute to indigo bunting population decline. Because they breed and sing along roadsides, many are killed by vehicle collisions in summer. During migration, many die after flying into buildings and transmission towers. Additionally, in wintering ground regions, they are trapped for the Illegal caged bird trade as well as hunted.