Also known as hammerkop, hammerkopf, hammerhead, hammerhead stork, umbrette, umber bird, tufted umber, or anvilhead, is a medium-sized wading bird 56 centimetres (22 in) in length with a weight of 470 grams (17 oz). The shape of its head with a long bill and crest at the back is reminiscent of a hammer, hence its name. Its plumage is a drab brown with purple iridescence on the back (the subspecies S. u. minor is darker). The bill is long, flat, and slightly hooked. The neck and legs are shorter than those of most of the Ciconiiformes. The hamerkop has, for unknown reasons, partially webbed feet. The middle toe is comb-like (pectinated) like a heron's. Its tail is short and its wings are big, wide, and round-tipped; it soars well. When it does so, it stretches its neck forward like a stork or ibis, but when it flaps, it coils its neck back something like a heron.
Habitat and Distribution
The hamerkop occurs in Africa south of the Sahara, Madagascar and coastal south-west Arabia in all wetland habitats, including irrigated land such as rice paddies, as well as in savannahs and forests. Most are sedentary within their territories, which are held by pairs, but some migrate into suitable habitat during the wet season only. Whenever new bodies of water are created, such as dams or canals, hamerkops quickly move in.
Hamerkops feed during the day, often taking a break at noon to roost. They normally feed alone or in pairs. The food is typical of long-legged wading birds, and the most important is amphibians. They also eat fish, shrimp, insects and rodents. They walk in shallow water looking for prey, shuffling one foot at a time on the bottom or suddenly opening their wings to flush prey out of hiding. The same shuffling technique is used to locate food in middens of fish remains.
The strangest aspect of hamerkop behaviour is the huge nest, sometimes more than 1.5 metres (4 ft 11 in) across, comprising perhaps 10,000 sticks and strong enough to support a man's weight. At the finished nest, a pair gives displays similar to those of the group ceremonies and mates, often on top of the nest. The clutch consists of three to seven eggs which start white but soon become stained. Both sexes incubate for 28 to 30 days. Both feed the young, often leaving them alone for long times; this unusual habit for wading birds may be made possible by the thick nest walls. The young hatch covered with grey down. By 17 days after hatching, their head and crest plumage is developed, and in a month, their body plumage. They leave the nest at 44 to 50 days but roost in it at night until about two months after hatching.
Calls and Songs
Vocalisations include cackles and a shrill call given in flight. Hamerkops are mostly silent except when in groups.