Juvenile (First Basic plumage): In most subspecies (other than northern minimus), shows sexual dimorphism in First Basic plumage; this is the only species of cowbird that is dimorphic at this stage (Jaramillo and Burke 1999).
Male. Varying from dark chaetura drab to fuscous black on upperparts; wing coverts margined with dusky grayish brown, creating 2 wing-bars; underparts dull buffy-gray, heavily streaked with sooty grayish-brown to fuscous black. Abdomen washed with yellowish buff. As in Brown-headed Cowbird (Molothrus ater), underwing coverts of Juvenile male may average darker than those of Juvenile female (Pyle 1997).
Female. Varying from light tawny olive to buffy brown; wing coverts margined with grayish tawny, creating 2 wing-bars; underparts varying from dull light buffy to light grayish, slightly washed with buffy and distinctly, but not always conspicuously, streaked with light grayish brown.
