Although there are numerous species of larks, most of them have in common what is known as a "larkspur," a long, straight claw on the hind toe. These roughly sparrow-sized birds are known for their elaborate, melodious songs and their flamboyant song-display flights during mating season. Because they nest on the ground, larks have evolved into fairly dull-looking birds as protection against predators, animals that hunt them for food. They generally vary in color from brown to pinkish-buff to gray, although some sport more distinguished markings and colors. Usually their upper bodies are heavily streaked or unmarked with a grayish brownish color that closely matches the soil in their specific habitats. Their breasts and underparts are often lighter in color and unmarked. Larks range widely in size from 3.9 to 9 inches (10 to 23 centimeters) and can weigh from just under half an ounce to 2.6 ounces (12 to 73 grams). In most species both sexes look very similar, although the males are often larger than the females.
Some types of larks, most notably the crested lark, have tiny crown feathers that they can raise into a crest, while others, like the horned lark, have small tufts that stand out on the sides of their heads, giving them a horned appearance. In addition, there are almost as many different kinds of bills among larks as there are species. They range in shape from long, thin, and pointed to cone-shaped, short, and thick, depending on the main food source and feeding methods to which a local species has adapted. Most larks have short legs and strong feet for scratching in the dirt, along with a hind toe that is much longer than the front ones. However, some larks, depending on whether they are fast runners or live on hard-packed dirt, have shorter spurs.
After they hatch, baby larks are covered with a thin, fine down. As they mature, they develop a uniformly spotted plumage that conceals them from predators. Unlike other similar birds species, larks grow their mature plumage as soon as they leave the nest and are able to live on their own.