thumb|[[Queen Elizabeth National Park, Uganda]]

The hamerkop (Scopus umbretta), also called the umbrette, is a medium-sized bird. It is the only living species in the genus Scopus and the family Scopidae. The species and family was long thought to sit with the Ciconiiformes but is now placed with the Pelecaniformes, and its closest relatives are thought to be the pelicans and the shoebill. 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 a medium-sized waterbird with brown plumage. 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 is a sedentary bird that often shows local movements.

The hamerkop takes a wide range of prey, mostly fish and amphibians, but shrimps, insects and rodents are taken too. Prey is usually hunted in shallow water, either by sight or touch, but the species is adaptable and will take any prey it can. The species is renowned for its enormous nests, several of which are built during the breeding season. Unusually for a wading bird, the nest has an internal nesting chamber where the eggs are laid. Both parents incubate the eggs and raise the chicks.

The species is not globally threatened and is locally abundant in mainland Africa and Madagascar. The International Union for Conservation of Nature (IUCN) has assessed it as being of least concern.

Taxonomy and systematics

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. The species was subsequently described and illustrated by French polymath Comte de Buffon. 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. He placed the species in the genus Scopus that had been introduced by Brisson and coined the binomial name Scopus umbretta.

Brisson's names for bird genera were widely adopted by the ornithological community despite the fact that he did not use Linnaeus' binomial system. The International Commission on Zoological Nomenclature ruled in 1911 that Brisson's genera were available under the International Code of Zoological Nomenclature, so Brisson is considered to be the genus authority for the hamerkop. The generic name, Scopus, is derived from the Ancient Greek for "shadow". The specific name umbretta is modified from the Latin for "umber" or "dark brown".

The hamerkop is sufficiently distinct to be placed in its own family, although the relationships of this species to other families has been a longstanding mystery. Recent studies have found that its closest relatives are the pelicans and shoebill. Although the hamerkop is the only living member of its family, one extinct species is known from the fossil record. 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. The hammerkop fossil record also includes fossil tracks from 90-130 thousand years ago.

The hamerkop is also known as the hammerkop, hammerkopf, hammerhead, hammerhead stork, umbrette, umber bird, tufted umber, or anvilhead.

Subspecies

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. That proposed subspecies was described by Austin L. Rand in 1936. It has also been suggested that birds near the Kavango River in Namibia may be distinct, but no formal description has been made.

Description

thumb|left|The subspecies S. u. minor is smaller and darker.

The hamerkop is a medium-sized waterbird, standing high and weighing , although the subspecies S. u. minor is smaller. Its plumage is a drab brown with purple iridescence on the back; S. u. minor is darker. The tail is faintly barred with darker brown. The sexes are alike and fledglings resemble adults. The bill is long, , and slightly hooked at the end. It resembles the bill of a shoebill, and is quite compressed and thin, particularly at the lower half of the mandible. The bill is brown in young birds, but becomes black by the time a bird fledges. The middle toe is comb-like (pectinated) like a heron's.

Distribution and habitat

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. In Tanzania, it has also recently begun to feed on rocky shores. Most are sedentary within their territories, which are held by pairs, but some migrate into suitable habitat during the wet season only. The species is very tolerant of humans and readily feeds and breeds in villages and other human-created habitats. Dominant birds may signal to subordinates by opening their bills slightly and erecting their crests, but the species is not very aggressive in general towards others of its species. Birds in groups also engage in social allopreening. One bird presents its face of back of the head to the other to be preened.

This species has been recorded foraging for insects flushed by grazing cattle and buffalo, It has also been recorded feeding in association with banded mongooses; when a band of mongooses began hunting frogs in dried mud at the side of a pool of water a pair of hamerkops attended the feeding group, catching frogs that escaped the mongooses.

Breeding

thumb|right|Full view of nest built in the fork of an acacia tree

The strangest aspect of hamerkop behaviour is the huge nest, sometimes more than across, and strong enough to support a man's weight. When possible, it is built in the fork of a tree, often over water, but if necessary, it is built on a bank, a cliff, a human-built wall or dam, or on the ground. A pair starts by making a platform of sticks held together with mud, then builds walls and a domed roof. A mud-plastered entrance wide in the bottom leads through a tunnel up to long to a nesting chamber big enough for the parents and young. Barn owls and eagle owls may force them out and take over the nests, but when the owls leave, the pair may reuse the nest. as may snakes, small mammals such as genets, and various birds, and weaver birds, starlings, and pigeons may attach their nests to the outside. Even where pairs have home ranges that are more spread out those home ranges overlap and are the boundaries are poorly defined.

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. Pairs engage in a breeding display, then copulate on the nest or on the ground nearby. The clutch consists of three to seven eggs which start chalky white, but soon become stained.

It is known in some cultures as the lightning bird, and the Kalahari Bushmen believe or believed that being hit by lightning resulted from trying to rob a hamerkop's nest. They also believe that the inimical god Khauna would not like anyone to kill a hamerkop. According to an old Malagasy belief, anyone who destroys its nest will get leprosy, and a Malagasy poem calls it an "evil bird". Such beliefs have given the bird some protection. A south African name Njaka meaning "rain doctor" is derived from its habit of calling loudly prior to rain.

Scopus, a database of abstracts and citations for scholarly journal articles, received its name in honour of this bird, as did the journal of the East African Natural History Society, Scopus.

References

  • Hamerkop - The Atlas of Southern African Birds
  • Hamerkop Structured guide to the species in southern Africa