About Leucocarbo verrucosus (Cabanis, 1875)
Leucocarbo verrucosus, commonly known as the Kerguelen shag, is the smallest species of blue-eyed shag. Adults measure 65 cm (25.5 in) in length with a 110 cm (43.5 in) wingspan. The adult's upperparts, tail, and thighs are metallic greenish black; the underbody extending up to the throat is white; and the wing linings are brown. Some individual Kerguelen shags have white patches on their back and wings. The head and back of the neck are deep blue or purple, with a black cap that extends below the eye to the chin and ear coverts. The face and throat pouch are dark brown, decorated with yellow-orange tubercles. The bill is either horn-colored or brown, and the eyes are hazel. Legs and feet range from dark brown to bright pink with dark blotches. Breeding adults have a small erectile black crest on the forehead, yellow or orange caruncles (large warts) above the base of the bill, and a bright blue ring around the eye. After the breeding season, plumage fades, the eye-ring changes to lead-blue, and the caruncles become smaller and duller in color. Juveniles are dark brown with varying amounts of white on their undersides, and have brown irises, bills, and feet. They do not have caruncles, and their eye-rings are lead-blue. They develop adult plumage gradually. Unlike many cormorant species, the Kerguelen shag does not spread its wings while perched. This species nests along the coast of Grande Terre, the main island of the Kerguelen archipelago, as well as on offshore islands and islands within the Golfe du Morbihan. It forages at sea throughout the archipelago, usually staying within 6 km (3.7 mi) of shore and favoring bays and inlets, though immature individuals have rarely been sighted as far as 80 km (50 mi) from shore. Reports of this species from Heard Island and western Australia are likely of birds that traveled there with assistance from ships. During the austral summer, it feeds among kelp, sometimes at the kelp bed bottom. The Kerguelen shag breeds in colonies, which typically contain 3 to 30 pairs, but can occasionally hold up to 400 pairs. Colonies may be located near colonies of southern rockhopper penguins. A period of nest building and courtship displaying occurs in late March and early April, which is an unusual timing for a subantarctic cormorant. Advertising males display by throwing their head backward until the nape touches their tail. Nests are cone-shaped structures built from seaweed, twigs, and grass bound together with mud and guano. They can grow up to 1 meter tall and 33 cm across, with an interior cup that averages 20 cm across and 8 cm deep. Surviving nests may be reused, though not necessarily by the same breeding pair. Breeding activity can begin as early as September, but egg laying usually starts between late October and late November and continues until mid-January, with timing varying considerably between different colonies. A clutch holds two to four eggs, which measure about 6.2 cm long and 3.9 cm wide. The second egg is laid 2 to 3 days after the first. Both parents incubate the eggs for an average of 29 days. Both parents also protect chicks from predators including skuas, gulls, and sheathbills, though these predators still catch some chicks. Newly hatched chicks are black with a pink throat, and later develop blackish-brown down with greyish-white tufts. Other details of the species' reproductive behavior and breeding success have not been documented. Between 1984 and 1987, the total population was estimated at 6,000 to 7,000 breeding pairs. Interactions with humans and introduced mammals do not appear to be harming the species' population.
