The hamerkop (Scopus umbretta), also known as hammerhead stork, umbrette and anvilhead, is a unique and widespread species of bird thought to be distantly related to pelicans. It is a medium-sized bird measuring up to 56 cm (22 in) in length and weighing up to 470 g (17 oz). It is named after its uniquely shaped head, which resembles a hammer. The hamerkop has a uniformly brown plumage, a long and straight black beak, and black legs. Its appearances cannot be confused with any other species. When in flight the hamerkop folds its neck like a heron when flapping its wings, but will extend it like a stork when soaring.
Hamerkops are always found close to water and can be found in any wetland habitat. They are not picky about their habitat as long as there is some form of water body present and can therefore be found in anything from open savannahs to dense forests. It is not particularly common in arid regions. The hamerkop is a carnivorous bird, with amphibians the main food source. It will also eat fish, insects, shrimps, and small mammals. It will typically look for food in shallow water, using its feet or wings to flush prey out of its hiding place. It forages alone or in pairs.
The hamerkop is an unusual bird exhibiting behaviour not seen in any other bird. Even though this bird typically lives alone or in pairs it sometimes joins in rituals or courtship displays with other individuals. In these rituals they will run in circles around each other while they raise their crests, flutter their wings and make loud calls. Up to ten birds have been observed to partake in this strange behaviour together. They also have a tendency to mount or stand on top of other individuals without trying to copulate. This is called “false mounting” and might be a way of showcasing dominance.
Another unusual aspect of hamerkop behaviour is their nest building. A breeding pair typically build the nest together, but as many as seven individuals have been observed building one nest. They build massive nests that can be 1.5 meters (4 ft 11 in) across, almost 2 meters (6 ft 7 in) deep, and weigh up to 50 kg (110 lb). A nest is usually strong enough to support the weight of a man. The nest is made up of thousands of sticks, stalks, twigs, reeds, and grass glued together with mud. The eggs are laid in a hollow area within the nest, which can be reached through a side entrance. Colorful and shiny objects, both natural and man-made, are used to decorate the outside.
One nest can take from 40 days to several months to build. It is usually built in the fork of a tree next to water, but occasionally also on bridges, dams, walls, houses, and sometimes even on the ground. The hamerkop is a compulsive nest builder and will construct three to five nests per year, even when it is not breeding. Not all nests will be used for breeding purposes. When a nest is finished the breeding pair will do a similar ritual to the one mentioned above on top of the nest. Nests that are not used by the hamerkop will often be taken over and used as housing by other animals, such as reptiles or genets, or as nests by other birds, such as barn owls or black sparrowhawks.
Because the hamerkops typically live in lush and water rich environments, breeding season can be almost year-round. The female will lay three to nine eggs, which will be incubated by both parents for 26-30 days. Both sexes take part in feeding the chicks, but they often leave the chicks unguarded for long periods. This is probably made possible because of the thick walls of the large nest protecting the chicks inside. The head and crest plumage is developed after 17 days, and the body plumage after a month. The chicks leave the nest after 44-50 days, and will be strong flyers a few days later. They will use the nest as an overnight roosting site for about two more months.
The hamerkop is a widespread and very common bird who is likely to have benefited from human expansion and man-made water bodies. It is listed as least concern on the IUCN Red List. The hamerkop is a common bird in myths and legends in a lot of African cultures, which has helped to protect it. The bushmen of the Kalahari have named it the “lightning bird” and believe that any man who tries to steal the hamerkop’s eggs will be struck by lightning. The Malagasy people of Madagascar believe one will get leprosy by destroying a hamerkop’s nest and believe the bird to be evil.