Hamerkop
Hamerkop | |
---|---|
In Kenya | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Pelecaniformes |
Family: | Scopidae |
Genus: | Scopus |
Species: | S. umbretta
|
Binomial name | |
Scopus umbretta Gmelin, 1789
| |
Range of the hamerkop |
The hamerkop (Scopus umbretta) is a medium-sized wading
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 Africa and Madagascar, and 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.[2] The species was subsequently described and illustrated by French polymath Comte de Buffon.[3][4] When the German naturalist Johann Friedrich Gmelin revised and expanded Carl 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.[5]
Brisson's names for bird
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 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
Description
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. 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 resembled adults.[10] The bill is long, 80 to 85 mm (3.1–3.3 in), 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.[10]
The neck and legs are proportionately shorter than those of similar looking Pelecaniformes. The bare parts of the legs are black and the legs are feathered only to the upper part of the tibia. The hamerkop has, for unknown reasons, partially webbed feet.[18] The middle toe is comb-like (pectinated) like a heron's.[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.[10] 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.[18] Its gait when walking is jerky and rapid, with its head and neck moving back and forth with each step. It may hold its wings out when running for extra stability.[19]
Distribution and habitat
The hamerkop occurs in
Behaviour and ecology
The hamerkop is mostly active during the day, often resting at noon during the heat of the day. They can be somewhat crepuscular, being active around dusk, but are not nocturnal as has sometimes been reported.[10]
Social behaviour and calls
The hamerkop is mostly silent when alone, but is fairly vocal when in pairs or in groups. The only call it usually makes when alone is a flight-call, a shrill "nyip" or "kek". In groups,
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.
Food and feeding
This species normally feeds alone or in pairs, but also feeds in large flocks sometimes. It is a generalist, although amphibians and fish form the larger part of its diet. The diet also includes shrimp, insects, and rodents. 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. Because it is willing to take a wide range of food items and also take very small prey, it is not resource-limited and only feeds for part of the day.[10]
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.[19] It may shuffle one foot at a time on the bottom or suddenly open its wings to flush prey out of hiding.[18][19] 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.[19] It is also opportunistic, and feeds on swarming termites when they conduct their nuptial flights, snatching as many as 47 alates (flying termites) in five minutes.[22]
This species has been recorded foraging for insects flushed by grazing cattle and buffalo,[10][23] in a manner similar cattle egrets, and has been observed fishing off the backs of hippopotamuses.[23] 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.[24]
Breeding
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. 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 13–18 cm (5.1–7.1 in) wide in the bottom leads through a tunnel up to 60 cm (24 in) long to a nesting chamber big enough for the parents and young.[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. 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.[19]
Pairs of hamerkop are compulsive nest builders, constructing three to five nests per year whether they are breeding or not.
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.[10] The eggs measure 44.5 mm × 33.9 mm (1.75 in × 1.33 in) on average, and weight around 27.8 g (0.98 oz), but considerable variation is seen. Egg size varies by season, by the overall size of the clutch, and from bird to bird.[25] Both sexes incubate the eggs, but the female seems to do the 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.[10]
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.[18]
Relationship with humans
Many legends exist about the hamerkop. In some regions, people state that other birds help it build its nest.[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.[29]
It is known in some cultures as the
Scopus, a database of abstracts and citations for scholarly journal articles, received its name in honour of this bird,[34] as did the journal of the East African Natural History Society, Scopus.[35]
References
- . Retrieved 19 November 2021.
- ^ Brisson, Mathurin Jacques (1760). Ornithologie, ou, Méthode contenant la division des oiseaux en ordres, sections, genres, especes & leurs variétés (in French and Latin). Paris: Jean-Baptiste Bauche. Vol 1 p. 48, Vol 5 p. 503.
- ^ Buffon, Georges-Louis Leclerc de (1780). "L'Ombrette". Histoire Naturelle des Oiseaux (in French). Vol. 7. Paris: De l'Imprimerie Royale. p. 278.
- Daubenton, Louis-Jean-Marie (1765–1783). "L'Ombrette, du Sénégal". Planches Enluminées D'Histoire Naturelle. Vol. 8. Paris: De L'Imprimerie Royale. Plate 796.
- ^ Gmelin, Johann Friedrich (1788). Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1, Part 2 (13th ed.). Lipsiae [Leipzig]: Georg. Emanuel. Beer. p. 618.
- hdl:2246/678.
- ^ Hemming, Francis, ed. (1958) [1911]. "Opinion 37: Shall the genera of Brisson's "Ornithologia," 1760, be accepted". Opinions and Declarations Rendered by the International Commission on Zoological Nomenclature. Vol. 1 Section B. London: International Trust for Zoological Nomenclature. pp. 87–88.
- ^ China, W.E. (1963). "Direction 105: Brisson, 1760, Ornithologie: restriction to certain portions of that work of the validation granted under the Plenary Powers". Bulletin of Zoological Nomenclature. 20 (5): 343–344.
- ISBN 978-1-4081-2501-4.
- ^ S2CID 243232039. Retrieved 8 July 2017.
- PMID 11429133.
- PMID 17148284.
- PMID 32781465.
- ISSN 0006-324X.
- Rasmussen, Pamela, eds. (August 2022). "Ibis, spoonbills, herons, Hamerkop, Shoebill, pelicans". IOC World Bird List Version 12.2. International Ornithologists' Union. Retrieved 2 December 2022.
- ^ S2CID 242907842. Retrieved 18 June 2017.
- ^ Clancey, P. A. (1982). "Namibian Ornithological Miscellanea" (PDF). Durban Museum Novitates. 13 (6): 55–63.
- ^ ISBN 978-81-261-0967-8. Retrieved September 25, 2008.
- ^ .
- ISBN 978-0-7136-7602-0.
- doi:10.1002/fee.1318.
- JSTOR 2388744.
- ^ .
- .
- ^ .
- .
- .
- ^ Kaweesa, Sarah; Jonkvorst, Robert; Katebaka, Raymond; Ssemmanda, Richard; Pomeroy, Derek; Brouwer, Joost (2013). "Is the Hamerkop Scopus umbretta a neocolonist or an opportunist nester?". Scopus. 32: 35–38.
- ISBN 9780710020819. Retrieved September 22, 2008.
- ^ Schapera op. cit., p. 189
- ISBN 978-0-8387-5175-6.
- ISBN 978-0-412-79730-9.
- ^ Kennedy, R.J. (1970). "Direct effects of rain on birds: a review" (PDF). British Birds. 63 (10): 401–414.
- PMID 16522216.
- ^ "Publications: Scopus". Nature Kenya. Bird Committee of the East Africa Natural History Society. Retrieved 9 March 2019.
External links
- Explore Species: Hamerkop at eBird (Cornell Lab of Ornithology)