The shape of its head with a long bill and crest at the back is reminiscent of a hammer, which has given this species its name after the Afrikaans word for hammerhead.

It is found in mainland Africa, Madagascar and Arabia, living in a wide variety of wetlands, including estuaries, lakesides, fish ponds, riverbanks, and rocky coasts.

The hamerkop takes a wide range of prey, mostly fish and amphibians, but shrimps, insects and rodents are taken too.

The hamerkop was first described by the French zoologist Mathurin Jacques Brisson in 1760 in his landmark Ornithologia, which was published two years after the tenth edition of Carl Linnaeus' Systema Naturae.

[3][4] When the German naturalist Johann Friedrich Gmelin revised and expanded Linnaeus's Systema Naturae in 1788 he included the hamerkop and cited the earlier authors.

[5] Brisson's names for bird genera were widely adopted by the ornithological community despite the fact that he did not use Linnaeus' binomial system.

Scopus xenopus was described by ornithologist Storrs Olson in 1984 based on two bones found in Pliocene deposits from South Africa.

Scopus xenopus was slightly larger than the hamerkop and Olson speculated based on the shape of the tarsus that the species may have been more aquatic.

Two subspecies are recognized—the widespread nominate race S. u. umbretta and the smaller of West African S. u. minor, described by George Latimer Bates in 1931.

It has also been suggested that birds near the Kavango River in Namibia may be distinct, but no formal description has been made.

[17] The hamerkop is a medium-sized waterbird, standing 56 cm (22 in) high and weighing 470 g (17 oz), although the subspecies S. u. minor is smaller.

[10] Its tail is short and its wings are big, wide, and round-tipped; it soars well, although it does so less than the shoebill or storks.

[19] The hamerkop occurs in Africa south of the Sahara, Madagascar, and coastal south-west Arabia.

It requires shallow water in which to forage, and is found in all wetland habitats, including rivers, streams, seasonal pools, estuaries, reservoirs, marshes, mangroves, irrigated land such as rice paddies, savannahs, and forests.

This call is made with the neck extended and sometimes accompanied by wing flapping, and becomes more vigorous when larger numbers of birds are present.

The type of food they take seems to vary by location, with clawed frogs and tadpoles being important parts of the diet in East and Southern Africa and small fish being almost the only prey taken in Mali.

[19] It may shuffle one foot at a time on the bottom or suddenly open its wings to flush prey out of hiding.

A bird flies slowly low over the water with legs dangling and head looking down, then dipping feet down and hovering momentarily when prey is sighted.

[24] The strangest aspect of hamerkop behaviour is the huge nest, sometimes more than 1.5 m (4 ft 11 in) across, and strong enough to support a man's weight.

A pair starts by making a platform of sticks held together with mud, then builds walls and a domed roof.

[18] Nests have been recorded to take between 10 and 14 weeks to build, and one researcher estimated that they would require around 8,000 sticks or bunches of grass to complete.

Much of the nesting material added after completion is not sticks, but an odd collection of random items including bones, hide, and human waste.

[25] Breeding happens year-round in East Africa, and in the rest of its range, it peaks at different times, with a slight bias towards the dry season.

[18] The ǀXam informants of Wilhelm Bleek said that when a hamerkop flew and called over their camp, they knew that someone close to them had died.