Hamerkop

Hamerkop
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Pelecaniformes
Family: Scopidae
Bonaparte, 1849
Genus: Scopus
Brisson, 1760
Species: S. umbretta
Binomial name
Scopus umbretta
Gmelin, 1789
Range of the hamerkop

The hamerkop (Scopus umbretta), is a medium-sized wading bird. It is the only living species in the genus Scopus and the family Scopidae. 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. It ranges from Africa, Madagascar to Arabia, in wetlands of a wide variety, including estuaries, lakesides, fish ponds, riverbanks and rocky coasts in Tanzania. The hamerkop, which is a sedentary bird that often show local movements, is not globally threatened and is locally abundant in Africa and Madagascar.

Taxonomy and systematics

The hamerkop was first described by the French zoologist Mathurin Jacques Brisson in 1760 in his landmark Ornithologia, published two years after Carl Linnaeus' sixth edition of the Systema Naturae. Brisson's work was later incorporated by Linnaeus into his later editions, and Brisson's names for bird genera were widely adopted by the ornithological community. This is despite the fact that Brisson for the most part named only genera and rarely named species.[2] The International Commission on Zoological Nomenclature (ICZN) ruled in 1911 that although the Brisson's genera lacked species names, they were available under the International Code of Zoological Nomenclature,[3][4] so Brisson is considered to be the genus author for the hamerkop. The specific name was given to the hamerkop in 1788 by the German naturalist Johann Friedrich Gmelin.[5]

The hamerkop is sufficiently distinct to be given its own family, although the relationships of this species to other families has been a longstanding mystery.[6] The hamerkop is usually included in the Ciconiiformes, but might be closer to the Pelecaniformes.[7] Recent studies have found that its closest relatives are the pelicans and shoebill.[8]

The hamerkop is the only living member of its family, but one extinct species is known from the fossil record. Scopus xenopus was described by ornithologist Storrs Olson in 1984 from Pliocene deposits found in South Africa.[9]

The generic name, Scopus, is derived from the Ancient Greek skia for shadow.[10] The specific name umbretta is modified from the Latin for umber or dark brown.[11] The hamerkop is also known as the hammerkop, hammerkopf, hammerhead, hammerhead stork, umbrette, umber bird, tufted umber, or anvilhead.

Subspecies

There are two subspecies currently recognised. The widespread nominate race S. u. umbretta, and the smaller of West African S. u. minor, described by George Latimer Bates in 1931.[5] Two other subspecies have been proposed. S. u. bannermani of south west Kenya is usually lumped with the nominate race. It has been suggested that birds in Madagascar may be distinct, in which case they would be placed in the subspecies S. u. tenuirostris.[5] 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.[12]

Description

The subspecies S. u. minor is smaller and darker.

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.[6] 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 bottom mandible. The bill is brown in young birds but has become black by the time a bird fledges.[6]

Hamerkop in flight, with spread tail showing barring

The neck and legs are proportionately shorter than those of similar looking Ciconiiformes. 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.[13] The middle toe is comb-like (pectinated) like a heron's.[6] 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.[6] 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.[13] Its gait when walking is jerky and rapid, with its head and neck moving back and forth with each steps. It may hold its wings out when running for extra stability.[14]

Distribution and habitat

The hamerkop occurs in Africa south of the Sahara, Madagascar and coastal south-west Arabia. It requires shallow water to forage in, and is found in all wetland habitats, including rivers, streams, seasonal pools, estuaries, reservoirs, marshes, mangroves, irrigated land such as rice paddies, as well as in savannahs and forests. In Tanzania it has also recently begun to feed on rocky shores.[6] In Arabia it is found in rocky wadis with running water and trees.[15] 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 highly tolerant of humans and will readily feed and breed in villages and other human-created habitats.[6]

Behaviour and ecology

Hamerkops are 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.[6]

Social behaviour and calls

Hamerkops are mostly silent when they alone, but are 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, vocalisations include a range of calls including cackles and nasal rattles.[6] One highly social call is the "yip-purr" call. This call is only made in a social context, when at least three birds but up to twenty are gathered in a flock. Birds start by giving a number of "yip" calls, eventually giving way to purring notes. 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.[14]

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.[16] 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 will also engage in social allopreening when in groups. One bird will present its face of back of the head to the other to be preened.[14]

Food and feeding

Hammerkop eating a fish

Hamerkops normally feed alone or in pairs, but will also feed in large flocks sometimes. They are generalists, although amphibians and fish form the larger part of their diet. They also eat 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 they are willing to take a wide range of food items and also take very small prey, they are not resource limited and will only feed for part of the day.[6]

They walk in shallow water looking for prey. Prey is located differently depending on circumstances; if the water is clear they may hunt by sight, but if the water is very muddy they will probe their open bill into water or mud and shut it.[14] They may shuffle one foot at a time on the bottom or suddenly open their wings to flush prey out of hiding.[13][14] Prey caught in mud will be shaken before swallowing to clean it or, if available, taken to clearer water to clean. The species will also feed while in flight. Birds fly 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.[14] They are also opportunistic, and will feed on swarming termites when they conduct their nuptial flights, snatching as many as 47 alates (flying termites) in five minutes.[17]

Hamerkops have been recorded foraging for insects flushed by grazing cattle and buffalo,[6][18] in a manner similar cattle egrets, and have been observed fishing off the backs of hippopotamuses.[18] They have 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.[19]

Breeding

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 1.5 metres (4 ft 11 in) across, and strong enough to support a man's weight. The birds decorate the outside with any bright-coloured objects they can find. When possible, they build the nest in the fork of a tree, often over water, but if necessary they build 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 centimetres (5.1–7.1 in) wide in the bottom leads through a tunnel up to 60 centimetres (24 in) long to a nesting chamber big enough for the parents and young.[13] Nests have been recorded to take between 10 and 14 weeks to build, and one researcher estimated that they would require around 8000 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.[14]

Individual collecting nesting material at Lake Naivasha, Kenya

These birds are compulsive nest builders, constructing three to five nests per year whether they are breeding or not.[20] Both members of the pair build the nest, and it has been suggested that the building of nests has a function in creating or maintaining the pair bond between them.[21] Barn owls and eagle owls may force them out and take over the nests, but when the owls leave, the hamerkops may reuse the nests.[6] Owls may also use abandoned nests,[22] as may snakes, small mammals such as genets, and various birds, and weaver birds, starlings, and pigeons may attach their nests to the outside.[13] There have been a small number of reports of hamerkops nesting close together, including in Uganda where 639 nests in an 8 km2 (3.1 sq mi); even if each pair had made seven nests this would mean 8 pairs were nesting in that area. The species is not treated as colonial, as it does not habitually nest close together, but is not thought to be highly territorial either.[23] Even where pairs have home ranges that are more spread out those home ranges overlap and are the boundaries are poorly defined.[20]

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. Both sexes incubate the eggs, but it seems that the female does 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 hatch asynchronously.[6]

Both parents 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.[13]

Relationship with humans

There are many legends about the hamerkop. In some regions, people state that other birds help it build its nest.[13] 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.[24]

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.[25] According to an old Malagasy belief, anyone who destroys its nest will get leprosy, and a Malagasy poem calls it an "evil bird".[26] Such beliefs have given the bird some protection.[27]

Scopus, a database of abstracts and citations for scholarly journal articles, received its name in honour of this bird,[28] as did the journal of the East African Natural History Society, Scopus.

References

  1. ↑ BirdLife International (2016). "Scopus umbretta". IUCN Red List of Threatened Species. IUCN. 2016: e.T22697356A93610351. Retrieved 4 July 2017.
  2. ↑ Allen, J. A. (1910). "Collation of Brisson's genera of birds with those of Linnaeus" (PDF). Bulletin of the American Museum of Natural History. 28 (27): 317–335.
  3. ↑ 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. Volume 1 Section B. London: International Trust for Zoological Nomenclature. pp. 87–88.
  4. ↑ 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.
  5. 1 2 3 Elliott, A.; Garcia, E.F.J.; Boesman, P. (2017). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A.; de Juana, Eduardo, eds. "Hamerkop (Scopus umbretta)". Handbook of the Birds of the World Alive. Barcelona, Spain: Lynx Edicions. Retrieved 18 June 2017. (Subscription required (help)).
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Elliot, A. (2017). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A.; de Juana, Eduardo, eds. "Hamerkop (Scopidae)". Handbook of the Birds of the World Alive. Barcelona, Spain: Lynx Edicions. Retrieved 8 July 2017. (Subscription required (help)).
  7. ↑ Van Tuinen, Marcel; Butvill, Dave Brian; Kirsch, John A. W.; Hedges, S. Blair (2001). "Convergence and divergence in the evolution of aquatic birds" (PDF). Proceedings of the Royal Society of London. 26 (8): 1345–1350.
  8. ↑ Ericson, P. G. P.; Anderson, C. L.; Britton, T.; Elzanowski, A.; Johansson, U. S.; Källersjö, M.; Ohlson, J. I.; Parsons, T. J.; Zuccon, D.; Mayr, G. (2006). "Diversification of Neoaves: integration of molecular sequence data and fossils". Biology Letters. 2 (4): 543–547. PMC 1834003 Freely accessible. PMID 17148284. doi:10.1098/rsbl.2006.0523.
  9. ↑ Olson, Storrs (1984). "A Hamerkop from the early Pliocene of South Africa (Aves: Scopidae)" (PDF). Proceedings of the Biological Society of Washington. 97 (4): 736–740. ISSN 0006-324X.
  10. ↑ Jobling, J. A. (2017). "Key to Scientific Names in Ornithology: Scopus". Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 17 June 2017.
  11. ↑ Jobling, J. A. (2017). "Key to Scientific Names in Ornithology: umbretta". Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 17 June 2017.
  12. ↑ Clancey, P. A. (1982). "Namibian Ornithological Miscellanea" (PDF). Durban Museum Novitates. 13 (6): 55–63.
  13. 1 2 3 4 5 6 7 Shukla, Arvind N.; Tyagi, Rajiv (2004). Encyclopaedia of Birds. Anmol Publications PVT. LTD. p. 234. ISBN 81-261-0967-X. Retrieved September 25, 2008.
  14. 1 2 3 4 5 6 7 Kahl, M. P. (1967). "Observations on the behaviour of the Hamerkop Scopus umbretta in Uganda". Ibis. 109 (1): 25–32. doi:10.1111/j.1474-919X.1967.tb00004.x.
  15. ↑ Porter, Richard; Aspinall, Simon (2010). Birds of the Middle East (2nd ed. ed.). London: Christopher Helm. p. 60. ISBN 978-0-7136-7602-0.
  16. ↑ Hagemeyer, Natasha (2016). "Sex-obsessed or just sociable? Non-copulatory displays in the hamerkop". Frontiers in Ecology and the Environment. 14 (7): 397–398. doi:10.1002/fee.1318.
  17. ↑ Dial, K. P.; Vaughan, T. A. (1987). "Opportunistic Predation on Alate Termites in Kenya". Biotropica. 19 (2): 185. doi:10.2307/2388744.
  18. 1 2 Dean, W. R. J.; MacDonald, I. A. W. (2010). "A review of African birds feeding in association with mammals". Ostrich. 52 (3): 135–155. doi:10.1080/00306525.1981.9633599.
  19. ↑ Steyn, P (1991). "Hamerkops in Feeding Association with Banded Mongooses". Ostrich. 62 (1-2): 83. doi:10.1080/00306525.1991.9639643.
  20. 1 2 Wilson, R. T.; Wilson, M. P.; Durkin, J. W. (1987). "Aspects of the reproductive ecology of the Hamerkop Scopus umbretta in central Mali". Ibis. 129 (2): 382–388. doi:10.1111/j.1474-919X.1987.tb03182.x.
  21. ↑ Wilson, R.; Wilson, M. (1986). "Nest building by the Hamerkop Scopus umberetta". Ostrich. 57: 224–232.
  22. ↑ Martin, J.; Broekhuysen, G. J. (1961). "Some records of birds using the nests of others". Ostrich. 32 (3): 104–106. doi:10.1080/00306525.1961.9633083.
  23. ↑ 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.
  24. ↑ Schapera, Isaac (1965). The Khoisan Peoples of South Africa. G. Routledge and Paul. p. 167. Retrieved September 22, 2008.
  25. ↑ Schapera op. cit., p. 189
  26. ↑ Fox, Leonard (1990). Hainteny: The Traditional Poetry of Madagascar. Bucknell University Press. pp. 261, 422. ISBN 0-8387-5175-X.
  27. ↑ Child, Graham; Chitsike, Langford (August 31, 2000). "'Ownership' of Wildlife". In Prins, Herbert H. T.; Grootenhuis, Jan Geu; Dolan Thomas T. Wildlife Conservation by Sustainable Use. Netherlands: Springer. p. 253. ISBN 0-412-79730-5.
  28. ↑ Burnham, Judy F (8 March 2006). "Scopus database: a review". Biomedical Digital Libraries. 3 (1). doi:10.1186/1742-5581-3-1.
Wikispecies has information related to: Scopus umbretta
Wikimedia Commons has media related to Hamerkop.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.