Magellanic penguins' weights vary with the season. They tend to weigh the most directly prior to molt (which begins in March) since they are preparing to fast for the following few weeks. Males have a mean weight of 4.7 kg and females weigh a mean of 4.0 kg. The mean flipper length for males and females is 15.6 cm and 14.8 cm, respectively. The average beak length is 5.8 cm for males and 5.4 cm for females. Males and females have webbed feet that are, on average, 12.2 cm and 11.5 cm long, respectively. Adults and juveniles both have black bills, black backs, and white fronts. Adults have a symmetrical white band that originates at each eye, arches back on the sides of their heads, and comes together above their necks. Adults also have two black bands underneath their neck; juveniles only have one band. Juveniles display a range of white to dark gray patches on their cheeks. Juveniles have two layers of down before they develop their adult plumage.
Range mass: 2.5 to 7.5 kg.
Range length: 11.2 to 16.9 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger