Hammer head (bird)
| Hammer head | ||||||||||
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Hammerhead ( Scopus umbretta ) |
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| Systematics | ||||||||||
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| Scientific name of the family | ||||||||||
| Scopidae | ||||||||||
| Bonaparte , 1849 | ||||||||||
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| Scopus | ||||||||||
| Brisson , 1760 | ||||||||||
| Scientific name of the species | ||||||||||
| Scopus umbretta | ||||||||||
| JF Gmelin , 1789 |
The hammerhead or shadow bird ( Scopus umbretta ) is a water bird up to 56 cm in size that is widespread in sub- Saharan Africa. Because his closer relationships are unclear, he is usually assigned to a separate family Scopidae.
features
The name hammer head goes back to the unusual shape of the head: The species has an elongated beak and a rear-facing spring hood. The beak, which is relatively powerful in relation to its overall body size, is about 8 cm long, compressed at the sides and ends in a small hook. It is similar to the beak of the shoe bill , but is not quite as powerful.
There is no gender dimorphism . However, there are two subspecies that differ slightly in size and color (see systematics ). Hammer heads are up to 56 cm high and 470 g in weight. The plumage is brown and can take on a metallic sheen on the back.
The neck and legs are quite short, especially in comparison with many walking birds , in whose vicinity it was traditionally placed taxonomically. The wings are broad and rounded. They enable a fluttering flight with only rare gliding phases. In flight, the neck is stretched out like a stork.
distribution and habitat
The hammer head is widespread across wetlands in sub-Saharan Africa. Its vast distribution area also includes Madagascar as well as western Yemen and Saudi Arabia .
The bird can be found in all types of freshwater habitats. Lakes, rivers, swamps and also temporary water holes accommodate it when the water is shallow enough that it can run around in it. Sometimes hammerheads are also found in river deltas and mangroves . The prerequisite for a suitable habitat is the presence of trees that are used as nesting and resting places; only sometimes does the hammer head make do with other elevated places such as rocks.
The IUCN estimates the total population of the hammer head at 170,000 to 1.1 million animals. The hammer head is a common bird and is not considered endangered.
Way of life
activity
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The hammer head is a daytime and crepuscular bird that rests during the night and in the midday heat. He's a loner; it is only found in groups of up to fifty birds in the resting places.
nutrition
Most of the diet consists of fish and amphibians. The preferred fish include predatory catfish , barbel and tilapia , while clawed frogs and their tadpoles are particularly popular among the amphibians . Crustaceans, insects, worms and small mammals are also eaten to a lesser extent. To get to the prey, the hammer head digs up the bottom with its feet and pokes in the mud with its beak.
Occasionally one sees hammerheads flying over the water surface and catching fish and tadpoles in flight from the water. They also occasionally follow herds of cattle or buffalo to catch the insects they scare off.
Reproduction
The nest of the hammer head is extraordinary. It has a diameter of 1.5 m, consists of up to 8000 individual parts and is 100 times the weight of the bird. Both partners build it together, usually in a tree, sometimes on other elevated places such as clusters of rocks. Branches are piled on top of each other and glued together with mud. First the nest forms a platform, then the walls are built and finally a dome roof over the nest. The only access to the huge structure is on the underside. This entrance leads into a tunnel that is 10 to 15 cm wide and 40 to 60 cm long and at the end of which is the central nesting chamber with a diameter of 40 × 40 × 60 cm. A couple often builds several nests. These last for several years and can be used again and again. Expanding and mending the nests is a constant process that occurs in parallel with the brood.
The hammer head nest serves as a habitat for other animals. Small songbirds build their own nests on the outside of the huge nest, and, as further sub-tenant to find honeybees , genet , mongoose , monitor lizards , snakes , Egyptian Geese , bumps gloss geese , hawks , doves and black storks one - many of these but not simultaneously with a brooding hammerhead couple rather as an inhabitant of an abandoned nest.
The clutch consists of three to seven eggs, which both partners incubate for about 30 days. When the young hatch, they wear a gray downy dress that is replaced by feathers after a few days. The tufts form after six days, and after thirty days the young are very similar to adults, with the exception of the beak, which takes longer to reach its final size. Both partners feed the young, which fledged after around 47 days.
The broods are noticeably often unsuccessful. So 50% of the eggs should remain unhatched and 30 to 40% of the young birds should not survive. The main cause is the invasion of enemies, especially monitor lizards, into the nest.
Systematics
The classification of the hammer head has remained largely a mystery. Its beak bears a distant resemblance to that of the shoebill . On the basis of morphological analyzes, it was placed close to herons and flamingos , while an examination of the ectoparasites even suggested a relationship with the plovers . The most recent analyzes of the DNA revealed a new option: According to this, the hammer head is the sister species of a large taxon that is formed by the oarsopods (excluding tropical birds) and the shoebill. This result calls into question the assignment of the hammer head to the walking birds.
SJ Hackett et al and Fain and Houde arrange the hammer head in its on DNA - sequence analysis based revision of the classification of birds as a sister species from the Pelikanen formed and the shoe beak taxon a.
According to the results of studies over the past twenty years, it has become questionable whether the shoebill could be attributed to the wading birds. A classification in the group of pelican relatives or in their vicinity is now far more likely. The following cladogram clarifies the current status (2018) of research on family relationships.
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The assignment of the hammer head to the Pelecaniformes has now been recognized by the International Ornithological Congress and included in its World Bird List.
There are at least two subspecies. The nominate form Scopus umbretta umbretta is widespread in central, eastern and South Africa as well as in Madagascar and western Arabia. In contrast, the subspecies Scopus umbretta minor lives in West Africa; it is somewhat smaller and has a noticeably darker plumage. Some authors also see Madagascar's hammerheads as a separate subspecies under the name Scopus umbretta bannermani .
swell
Much of the information in this article is taken from:
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 8487334105 .
The following sources are also cited:
- ↑ Scopus umbretta in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2009. Accessed November 13, 2011th
- ↑ Gerald Mayr: The phylogenetic affinities of the Shoebill (Balaeniceps rex) . In: Journal of Ornithology 2003, No. 144, pp. 157-175
- ↑ Hackett et al .: A Phylogenomic Study of Birds Reveals Their Evolutionary History . Science 27 June 2008: Vol. 320. no. 5884, pp. 1763–1768 doi : 10.1126 / science.1157704
- ^ Fain, MG, & P. Houde. 2004. Parallel radiations in the primary clades of birds. Evolution 58: 2558-2573
- ^ Brown, Joseph W. and John Harshman. 2008. Pelecaniformes. Version June 27, 2008. in The Tree of Life Web Project
- ^ Frank Gill and Minturn Wright: BIRDS OF THE WORLD Recommended English Names. Princeton University Press, 2006, ISBN 0713679042
- ↑ WorldBirdNames.org IOC World Bird List ( Memento of the original from February 18, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
Web links
- Scopus umbretta in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 7 of 2009.
- Videos, photos and sound recordings of Scopus umbretta in the Internet Bird Collection