Secretary (bird)
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Secretary ( Sagittarius serpentarius ) |
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| Systematics | ||||||||||||
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| Sagittariidae | ||||||||||||
| Finsch & Hartlaub , 1870 | ||||||||||||
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| Sagittarius | ||||||||||||
| Hermann , 1783 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Sagittarius serpentarius | ||||||||||||
| ( JF Miller , 1779) |
The secretary ( Sagittarius serpentarius ) is a large bird of prey that inhabits large parts of the African continent south of the Sahara . It inhabits open and semi-open savannah landscapes and feeds mainly on large insects and small mammals, which it kills with kicks on its long legs. But other small animals are also among its prey. Among other things, he is also able to hunt poisonous snakes. In areas with favorable conditions, some pairs occupy a territory for many years, elsewhere the species is highly nomadic. Breeding usually takes place in the rainy season when most of the food is available. Large nest platforms are then built in the crowns of low trees, similar to those of storks. The IUCN regards the species as endangered (“vulnerable”) due to the sharp decline in the population .
Because of its unique body structure, which is partly reminiscent of seriemas , bustards or cranes and distinguishes it from all other birds of prey, the secretary is placed in its own, monospecific family. Some authors even go so far as to assign it a separate order Sagitariiformes. Today, however, it is usually run as a separate family among the birds of prey (Accipitriformes).
description
The secretary is a very large bird of prey, often striding on the ground, which is reminiscent of bustards or cranes because of its long, stilt-like legs. With a height of about 1.20 m when standing, it is about the size of a crane . The body length is between 125 and 150 cm, the weight between about 2.3 and 4.3 kg. The wingspan is between 1.91 and 2.15 m, the wing length between 610 and 675 mm.
The relatively small head looks like an eagle with quite large eyes and a hook-shaped, blue-gray beak, yellow wax skin and a lively orange, bare skin area around the eye. In contrast to other birds of prey, the upper lids are long ciliate.
The neck plumage is elongated into a characteristic, long and thin hood that can be raised or placed on the neck. The individual feathers are black and spatulate towards the tip. Possibly the name “secretary” goes back to this characteristic, since the feathers of the hood look like quills stuck behind the ear.
The neck is quite short, so that the bird only reaches the intertarsal joint and has to bend down completely to reach the ground. The long, dark pink legs are feathered with black "trousers" up to the intertarsal joint. The tarsometatarsus is between 27.8 and 34.2 cm long and has strong, coarse scaling that protects the front in particular. The toes are short and strong with equally short, bent-down claws. They are only about a fifth the length of that of eagles of comparable size. The two outer front toes are of the same length and the rear toe is much smaller. The secretary cannot reach with his feet, but kills the prey with kicks or blows from above.
In flight, the secretary is almost unmistakable with a small head and an elongated neck. The wings are long and wide, with rounded ends, and are designed primarily for gliding. The wings of the hand are “fingered” like an eagle. The outer control springs are stepped so that they form a wedge over which the elongated middle pair protrudes by about 8 inches. They also protrude over the feet of the flying bird. The flapping flight is sluggish, slow and not very stimulating. Without sufficient thermals , the bird cannot hold out for too long. But if he is only in gliding, he is fast and agile.
The plumage is predominantly light gray on top. The black wings, the lower abdomen and the leg fletching contrast with this. The underside is otherwise white, as are the underwing , upper and lower tail covers . The control feathers are darkly clouded at the base and otherwise gray, with a wide black subterminal band and a white end border.
The sexes hardly differ. Males are slightly larger, on top a bit bluish gray with a longer hood. Young birds are shorter-tailed and have a shorter hood. The under wing and under tail coverts are banded gray-brown, the face is less intensely colored. Females in particular have brownish feather edges on their backs.
Portrait of a secretary with the conspicuous hood made of long neck feathers
The neck is quite short, so the bird has to bend down low to reach the ground.
Landing bird with spread feathers
Here you can see the short, strong toes with which the prey is killed when kicking.
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voice
The secretary is usually not very shouting. The most common call is a deep, throaty croak, which is also often lined up and which, when aroused, can escalate into a drawn-out, hoarse growl. Sometimes the head is thrown back. These sounds can mainly be heard during parade or during fights on the ground, but also when greeting the partner at the nest. Young people sometimes express them to enemies.
The alarm call is a simple, high-pitched croak. When threatened, deeper croaking sounds are made. At the nest, you can also hear soft cackling or deep whistles from the partners. Meowing or whistling noises have been observed in birds in the roost.
The begging call of the young birds is at first a soft squeaking, which as they grow up turns into a demanding cackle, meow or squeak and later into a scream. The calls can also often be heard at night.
distribution
The range of the secretary extends over large parts of the Afrotropis , whereby the species is absent in the rain forest belt, in the Horn of Africa and in Madagascar. It extends from southern Mauritania , Senegal , Gambia and northern Guinea eastwards through Mali , Burkina Faso , Ghana , Togo , Benin , the southern regions of Niger , Chad , Sudan and the northern regions of Nigeria , Cameroon and the Central African Republic to Ethiopia and to northwest Somalia . It runs southwards through the northeast and southeast of the Democratic Republic of the Congo , through Uganda , Kenya and Tanzania as well as from Angola , Zambia , Malawi and Mozambique to the Cape of Good Hope .
habitat
The secretary mainly inhabits open and semi-open savannah landscapes, but can also occasionally be found on cereal-growing areas and in semi-deserts with sparse vegetation. It is most common in relatively short-grass thorn bush savannahs with scattered umbrella acacias that can serve as a sleeping place or nest tree. The height of the grass is usually around 50 cm. Places with vegetation over 1 m high are avoided, as are areas that are too dense with bushes or rocky areas. In addition to the poor overview, there is a risk that the birds cannot fly up or run away quickly enough because of the obstacles. The species is therefore only rarely found in larger forest clearings. The altitude distribution ranges from above sea level to around 3000 m.
The secretary prefers clear savannah landscapes with rather low to medium-high vegetation.
Areas that are too dense with bushes are rather avoided, as the species there has trouble gaining height quickly enough.
Umbrella acacias are often used as sleeping and nesting places.
The species also occurs occasionally in semi-deserts.
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nutrition
The secretary feeds on small to medium-sized prey animals, which are killed with powerful kicks with the help of the short, robust and clawed toes. The size ranges from small butterflies to rabbits. In terms of numbers, insects such as beetles and grasshoppers represent the largest proportion, while the largest proportion in terms of weight is smaller mammals such as mice in particular , but also hedgehogs , mongooses , meerkats , squirrels and hares . In addition there are lizards , snakes , chameleons , small birds and young birds of larger species , Eggs, domestic chickens , amphibians , crabs and small turtles . Larger carcasses are of no interest to the species.
Food is only sought on the ground, whereby the bird can travel between 20 and 30 km per day. He walks - often with the hood upright - at a speed of about 3 km / h or 100 to 120 steps per minute and takes practically all suitable prey animals that come under his eyes. Sometimes he follows them in short sprints, opening the wings halfway to keep his balance. Every now and then he tries to startle prey by stamping on tufts of grass, for example. Bird nests with eggs or young are specifically searched for and cleared out. Here the bird does not step on the prey, but swallows it whole. Insects are rarely read from bushes. The secretary often hunts near bush fires, in which a number of fleeing small animals, but also carrion can be found.
The species is also capable of hunting poisonous snakes such as puff adders or cobras . They are killed with targeted kicks in the head, keeping their own head out of reach. Experiments with a bird in captivity have shown that the fatal kicks occur at a very high speed. The contact with the prey lasts 15 ms, only a tenth of the time of the blink of an eye of a human and takes place with a force of 195 Newtons , which corresponds to five times the body weight of the bird. Larger prey is sometimes held in place with the foot and torn apart with the beak, or hidden under bushes for a while to keep it in store. In general, however, the secretary chokes his prey down the very elastic gullet. Indigestible residues are choked out as bulges 40 to 45 mm in diameter and 30 to 100 mm in length. These are particularly common near sleeping places or nests, but can be strangled anywhere and anytime.
The secretary searches for his food exclusively on the ground and walks long distances.
Lizards also belong to its prey.
The prey is killed by powerful kicks.
The species can often be found hunting near areas of fire.
Reproduction
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The secretary's breeding season correlates in part with the rainy seasons, when most of the food is available in the savannah. But even outside of these, under favorable feeding conditions - for example in very humid years or with mass reproductions of rodents and grasshoppers - further broods can occur. In addition, there are pairs that deviate completely from the usual, regional breeding seasons. So one can count on breeding all year round in the entire distribution area; from Zambia, however, a main breeding season emerges with increasing clarity towards the south, which lies between August and March.
The size of the territory of a couple is mostly between 25 and 45 km², the distance between the nests of neighboring pairs between 4.5 and 15 km.
At the beginning of a brood, the birds are noticeable by their flight deck, where they circle high above the nest and call. During "shuttle flights", which can take up to 15 minutes, one or both partners drop in the air after braking, and then rise again and so on.
For nest building, the crown area of a tree is usually trampled flat and a platform between 1.5 and 2.5 m wide and 20 to 50 cm high is built from branches 3 to 7.5 m high. This is lined with blades of grass and tufts of grass, wool and animal manure. Nesting trees are often acacias, but other thorn bushes or trees such as firethorns or pines are also accepted. Sometimes old nests are reused, but often new ones are simply built - especially since the massive structures often collapse. Sometimes the construction activities can take up to six months without breeding if the conditions are not favorable. Both partners participate in nest building. Occasionally, the nests of lark-ears or steppe falcons are taken over.
The clutch consists of 1 to 3, in rare cases 4 eggs, which measure 78 × 56 mm and are speckled or speckled on an off-white or pale green-gray background. They are laid at intervals of 2 to 3 days and incubated by both partners between 42 and 46 days. The partners take turns up to six times a day. The nestling period is between 64 and 106 days, but usually lasts 75 to 90 days. The boys can remain dependent on their parents for another 62 to 105 days.
The breeding success can vary greatly. Sometimes there can only be one successful brood in six years, elsewhere 14 out of 26 broods were successful. Only rarely does it happen that three young fly out of a brood. In years with favorable conditions, another attempt at breeding can take place one month after a brood has taken place.
hikes
Due to the very changeable conditions within the distribution area, in which long dry seasons, the occurrence or absence of large numbers of grazing animals or bush fires are not uncommon, the species lives nomadically in many places. Under favorable conditions, pairs settle for many years, breed several times in a row and are then resident birds . Likewise, the birds can migrate in unfavorable years and the territories can only be reoccupied months or years later. In regions that are particularly hostile to life, the birds usually wander far and wide and only make individual attempts at breeding.
Inventory development
Due to strong population declines in the entire distribution area, the secretary is now classified as endangered (“vulnerable”) by the IUCN . There is no reliable information, but the number should not exceed several tens of thousands of pairs. The situation is particularly precarious in West Africa, where there have been no observations for years and the species is probably one of the most threatened birds of prey. In East and Northeast Africa the secretary is locally common. There are good stocks in protected areas, but also in the cultivated landscape with arable farming, where the species sometimes finds very favorable conditions. In many places, however, there are apparently also strong declines, mostly due to the negative effects of increasing settlement and land use. The species is usually not followed excessively, but is sensitive to disturbances.
Important measures for the conservation of the species would be comprehensive monitoring in order to be able to better assess the population numbers and population trends. In areas with strong declines, it is necessary to raise public awareness and investigate the causes more closely. Persecution, trapping and trading must be stopped where necessary.
Origin of names and culture
The origin of the term “secretary” is unclear, but probably goes back to the Boers , who named the bird as secretaris ( Dutch for secretary or privy councilor ) as early as the middle of the 18th century . In Afrikaans the species is still called sekretarisvoël , in Dutch secretarisvogel . The name probably refers to the long, spatula-shaped neck feathers, which look like quills stuck behind the ear, as well as the overall appearance, which has a certain resemblance to an early modern official in a frock coat .
The first printed description of the species from 1769 comes from the Dutch naturalist Arnout Vormaer (1720–1799), who had received a copy with the label Sagittarius from the Cape of Good Hope. He speculates that the name Sagittarius (= archer) describes the gait of the bird, which reminds of an archer sneaking up when hunting for prey. The common name secretarius in South Africa , on the other hand, is an unclean translation of the Latin term. Carl Peter Thunberg , who traveled to South Africa in 1772, wrote in 1788 that the local name was simply secretaris (not secretarius ). A relationship between the Dutch and the Latin word does not necessarily have to be present.
Other theories, according to which the word would be a Francophone corruption of the Arabic expression saqr-et-tair ( saqr = falcon, tair = bird), appear etymologically and historically implausible - on the one hand the designation makes no sense, on the other hand it is in older ones Sources nowhere to be found. The specific epithet serpentarius ( Latin serpens = snake) probably refers to the ability to hunt snakes.
The secretary is part of the coat of arms of South Africa and the coat of arms of Sudan .
literature
- James Ferguson-Lees , David A. Christie: Raptors of the World. Helm Identification Guides, Christopher Helm, London 2001, ISBN 0-7136-8026-1 .
- AC Kemp, Jr., Guy Kirwan, David Christie, Jeff Marks: Secretarybird (Sagittarius serpentarius) (1994/2014), in: J. del Hoyo, A. Elliott, J. Sargatal, AD Christie, E. de Juana (eds .): Handbook of the Birds of the World Alive , Lynx Edicions, Barcelona 2014
- AC Kemp: Family Sagittariidae (1994/2013), in: J. del Hoyo, A. Elliott, J. Sargatal, AD Christie, E. de Juana (eds.): Handbook of the Birds of the World Alive , Lynx Edicions, Barcelona 2014
Web links
- Sagittarius serpentarius in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2011. Accessed December 22, 2011th
- Videos, photos and sound recordings of Sagittarius serpentarius in the Internet Bird Collection
- Chim Diều Đại Chiến Rắn Hổ Mang , video on the hunting and breeding behavior of the secretary (Vietnamese sound)
Individual evidence
- ↑ AC Kemp: Family Sagittariidae (1994/2013), section Systematics , see literature
- ↑ Steven J. Portugal, Campbell P. Murn, Emily L. Sparkes, Monica A. Daley: The fast and forceful kicking strike of the secretary bird , Current Biology, Volume 26, Issue 2, pp. 58–59, January 2016, doi: 10.1016 / j.cub.2015.12.004 and Secretary Birds can kick a snake to death in the blink of an eye , press release of the Royal Veterinary College of January 25, 2016 (with video)
- ↑ a b c d A. C. Kemp: Family Sagittariidae (1994/2013), section Breeding , see literature
- ↑ a b c Ferguson-Lees / Christie: Raptors of the World (2001), p. 795, see literature
- ↑ a b c d A. C. Kemp et al .: Secretarybird (Sagittarius serpentarius) ( 1994/2014 ), section Breeding , see literature
- ↑ Ferguson-Lees / Christie: Raptors of the World (2001), p. 794, see literature
- ↑ AC Kemp: Family Sagittariidae (1994/2013), Movements section , see literature
- ↑ a b A. C. Kemp et al .: Secretarybird (Sagittarius serpentarius) ( 1994/2014 ), section Status and conservation , see literature
- ^ A b c Adrian Burton: Life Lines - The troublesome secretary of Suakin , In: Frontiers in Ecology and the Environment 12, 2014, p. 592
- ↑ JA Jobling: Key to Scientific Names in Ornithology (2015) in: J. del Hoyo, A. Elliott, J. Sargatal, AD Christie, E. de Juana (eds.): Handbook of the Birds of the World Alive , Lynx Edicions, Barcelona 2015