Overall, song sparrows are medium-sized, plump songbirds with rounded heads and long, rounded tails. Plumage varies based on geographical region. However, adults in many subpopulations have upper parts of their body that are chestnut brown or russet brown, with pale gray or creamy white chests and streaked breast with a characteristic dark breast spot.  

Among adults, length can range from 4.3-7.1 inches (11 to 18 centimeters), with a wingspan between 7.1 and 10 inches (18 to 25.4 centimeters) from tip to tip. 

Nesting grounds include open woodlands, shrubby fields and wet areas with dense foliage. They are also commonly found in areas with human development, like suburban parks or backyards.

Male song sparrows sing to attract females and to establish their territory, which they will defend against other males who intrude. They have a wide variety of vocalizations they use in their songs, which are a combination of repeated notes mixed with chips, trills and buzzes. Their songs differ based on their geographical region. 

Song sparrows forage for food on the ground or among vegetation, pecking and hopping while looking for small insects and seeds to eat. Their eating habits also vary based on geography. For example, populations that live among wetlands and coastal areas will search in very shallow water for small crustaceans, and sometimes fish, to eat. 

Male song sparrows establish territory during the nesting season, and do not like sharing with other males. However, these territories are relatively small so a resource-rich habitat will often contain many song sparrows living near one another.

Nests are usually constructed on the ground among shrubs or in a clump of weeds, although they will sometimes build nests higher off the ground.  Their nests are cup-shaped and are lined with twigs, grasses, leaves, and animal hair. Females lay clutches of between three and five eggs that are light colored with brown to red-brown spots. 

Females incubate the eggs for about 12-14 days. Both parents help with care and feeding for the nestlings, who are ready to leave the nest for the first time about 10 days after hatching, although they will remain with their parents for two to three more weeks before they are ready to live on their own.

Song sparrows are known to re-nest in the same location for multiple years.

Populations in North America appear to have declined since the 1960's, although they are still quite abundant. In addition to habitat loss, song sparrows are vulnerable to common threats like window strikes and predation from other animals, such as hawks and domestic cats.