Genovesa

With a wingspan of 1.5 meters, this species is the largest of the boobies. Its brilliant pure white body plumage contrasts with its almost black wing markings. Its stout bill is yellow-orange, set against a blue-black face mask. The juvenile birds look similar to those of the blue-footed booby, but the white of the underparts extends well up to the neck. Like the blue-foot, these birds nest on the ground. Because they are heavier and larger they have more trouble taking off. As a result, Nazca (this species was previously called "masked") booby colonies are usually found near cliffs and on the steep outer slopes of tuff and cinder cones. Here the upward air currents make it easier for these large birds to take off. This booby differs from the other two species of boobies found in Galapagos in that it has a more or less fixed annual breeding cycle. Hence, on any given island, breeding occurs at about the same time year after year, but from island to island the breeding season varies considerably.