The head, neck, back, and wings of greater roadrunners are dark brown-black and heavily streaked with white, while the breast is mostly white. The eyes are bright yellow and there is a postocular streak of bare blue and red skin. A particularly notable feature is the crest of black feathers, which is raised or lowered at will. Overall, the body has a streamlined appearance, with a long tail that may be carried at an upward angle. The legs and beak are blue. The feet are zygodactylous, with two toes pointed forward and two toes pointed backward. The sexes are similar in appearance. Immature greater roadrunners lack the colorful postocular streaks and are more bronze in color.

Greater roadrunners are medium-sized birds, weighing 227 to 341 g. An adult’s length is between 50 and 62 cm and the height is between 25 and 30 cm. Greater roadrunners have a wingspan of 43 to 61 cm.

Range mass: 227 to 341 g.

Range length: 50 to 62 cm.

Range wingspan: 43 to 61 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 1.4661 W.