Spectacled eiders are large sea ducks, 52 to 56 centimeters long (20 to 22 inches). In the winter and spring, adult males are in breeding plumage with a black chest, white back, and pale green head with a long, sloping forehead and white patches resembling spectacles around the eyes. During the late summer and fall, males are entirely mottled brown. Females and juveniles are mottled brown year�round with pale brown eye patches.