Northwestern crows are mid-sized birds, 41.9 to 44.5 cm long and weighing 340 to 440 g. They have a wingspan of about 99 cm and their feathers are iridescent black with bluish-violet on their head, neck, back, wings, and tail. Their eyes are a smokey brownish-grey color, and their bills are glossy and stout though smaller and less powerful than those of common ravens (Corvus corax). They also have bristlelike feathers covering the nares. Corvus caurinus has thick, black legs with large scales on the front side only. When at rest, the tips of their folded wings do not reach the tip of the tail, which has slightly rounded ends. The sexes look alike, though the male is slightly larger than the female.
Immature C. caurinus between 3 to 15 months are also black, but have less iridescence than adults. Their back, wing and tail feathers fade gradually from black to brown. Juveniles from 1 to 3 months have looser, fluffier feathers than adult or immature C. caurinus and their feathers are a dull black. They have blue eyes.
Corvus caurinus can be distinguished from American crows (Corvus brachyrhynchos) because it is about 10% smaller, with smaller feet. It is also smaller than common ravens (C. corax), and while C. corax has a wedge-shaped tail, the tail of C. caurinus is squarish. Corvus corax also has shaggy throat-feathers which C. caurinus lacks.
Range mass: 440 to 340 g.
Range length: 44.5 to 41.9 cm.
Average wingspan: 99 cm.
Sexual Dimorphism: male larger