The Northern Gannet (Morus bassanus) is the largest member of the gannet family, Sulidae. Young birds are dark brown in their first year, and gradually acquire more white in subsequent seasons until they reach maturity after five years. Adults are 81-110 cm (32-43 in) long, weigh 2.2-3.6 kg (4.8-7.9 lbs) and have a 165-180 cm (65-71 in) wingspan. Before fledging, the immature birds (at about 10 weeks of age) can weigh more than 4 kg (8.8 lbs). Their plumage is white with black wing tips. The bill is light bluish. The eye is light blue, and it is surrounded by bare, black skin. During breeding, the head and neck are brushed in a delicate yellow.