Product Code Database
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 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 , including estuaries, lakesides, fish ponds, riverbanks, and rocky coasts. The hamerkop is a sedentism 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.
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. The hamerkop was usually included in the Ciconiiformes, but is now thought to be closer to the Pelecaniformes. Recent studies have found that its closest relatives are the and shoebill. Although the hamerkop is the only living member of its family, one extinction 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 hamerkop is also known as the hammerkop, hammerkopf, hammerhead, hammerhead stork, umbrette, umber bird, tufted umber, or anvilhead.
Another common social behaviour is "false mounting", in which one bird stands on top of another and appears to mount it, but they do not copulate. This behaviour has been noted between both mated pairs and unmated birds, and even between members of the same sex and in reversed mountings, where females mount males. Because of this, the behaviour is thought to be social and not related to the pair bond. 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.
The usual method of hunting is to walk in shallow water looking for prey. Prey is located differently depending on circumstances; if the water is clear, it may hunt by sight, but if the water is very muddy, it probes its open bill into water or mud and shuts it. It may shuffle one foot at a time on the bottom or suddenly open its wings to flush prey out of hiding. Prey caught in mud is shaken before swallowing to clean it, or if available, taken to clearer water to do so. The species also feeds while in flight. 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. The prey is then snatched with the bill and swallowed in flight. This method of hunting can be very successful, with one birds catching prey on 27 of 33 attempts during one 45-minute session. It is also opportunistic, and feeds on swarming when they conduct their nuptial flights, snatching as many as 47 (flying termites) in five minutes.
This species has been recorded foraging for insects flushed by grazing cattle and buffalo, in a manner similar , and has been observed fishing off the backs of hippopotamuses. It has also been recorded feeding in association with ; 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.
Pairs of hamerkop are compulsive nest builders, constructing three to five nests per year whether they are breeding or not. Both members of the pair build the nest, and the building of nests may have a function in creating or maintaining the pair bond between them. 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. Owls may also use abandoned nests, as may snakes, small mammals such as genets, and various birds, and , starlings, and may attach their nests to the outside. A few reports exist of hamerkops nesting close together, including in Uganda, where 639 nests were seen in an area of ; even if each pair had made seven nests, this would mean 80 pairs were nesting in that area. The species is not treated as bird colony, as it does not habitually nest close together, but is not thought to be highly animal territory, either. 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. The eggs measure on average, and weight around , but considerable variation is seen. Egg size varies by season, by the overall size of the clutch, and from bird to bird. Both sexes incubate the eggs, but the female seems to do most of the work. Incubation takes around 30 days from the first egg being laid to hatching, eggs are laid with intervals of one to three days, and they hatch asynchronously.
Both parents feed the young, often leaving them alone for long times. This habit, which is unusual for wading birds, may be made possible because of 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 first leave the nest around 44 to 50 days after hatching, but continue to use the nest for roosting at night until they are two months old.
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.Schapera op. cit., p. 189 According to an old Malagasy people 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.
Breeding
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. 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. Nesting material may still be added by the pair after the nest has been completed and eggs have been laid. Much of the nesting material added after completion is not sticks, but an odd collection of random items including bones, hide, and human waste.
Relationship with humans
Many legends exist about the hamerkop. In some regions, people state that other birds help it build its nest. 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.
External links
|
|
