Rockhopper penguins measure about 55 centimeters in length and weigh around 2.5 kilograms. These birds stand upright on two short feet. Their legs are set far back on the body. The waterproof coat, composed of feathers that average 2.9 centimeters in length, is white on the underside and bluish-black on the top. The head has bright yellow plumage on the brow; the yellow feathers extend along the sides. The top of the head has spiked black feathers. The wings are strong, stiff, narrow and flipper-like. Rockhopper penguins have tiny eyes.
Range mass: 2000 to 3000 g.
Average length: 55 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike