The plumbeous vireo (Vireo plumbeus) is a small North American songbird, ranging from far southeastern Montana and western South Dakota south to the Pacific coast of Mexico, including the extreme southern regions of Baja California Sur. It is migratory, moving to the southern part of its range in winter, and its habitat generally encompasses open pine forests. The plumbeous vireo is 4.75 inches (12 cm) in length, with a gray head, back, and flanks, and whitish underparts. It has a solid white eye ring and white wing bars. The song, given persistently, consists of short, rough whistled phrases of several notes, spaced about 2 seconds apart. The phrases often alternate ending on a high note and a low note, giving an impression of question and answer. The plumbeous vireo builds a cup nest out of bark strips and down in the fork of a twig. It lays 3 to 5 white eggs with some brown spots. This species was formerly considered to belong to the same species as Cassin's vireo and blue-headed vireo. At that time, this complex of species was referred to as the "solitary vireo".