Short-toed eagle
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Short-toed Eagle ( Circaetus gallicus ) |
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| ( Gmelin , 1788) |
The Short-toed Eagle ( Circaetus gallicus ) is a rather large, langflügeliger representatives of the genus toed Eagle ( Circaetus ) within the family of Accipitridae (Accipitridae). The short-toed eagle is the only species of the genus that otherwise only occurs in sub-Saharan Africa that also breeds in Europe and Central Asia.
Among the European birds of prey, with its almost exclusively reptile food, it is a nutrition specialist and its occurrence is accordingly closely tied to a sufficient supply of snakes and lizards. The short- toed eagles that breed in the Palearctic are long-distance migrants with wintering areas in the Sahel region south of the Sahara . Despite a very large and partly highly fragmented range, no subspecies are currently generally recognized. After strong population declines in the 19th and early 20th centuries, the remaining stocks seem to be stable at a relatively low level at the moment.
Appearance
The short-toed eagle is quite a large bird of prey with a wingspan of up to 188 centimeters and a total length of 62–70 centimeters. In flight it looks a bit like a very bright common buzzard , but is significantly larger than it. Due to its size, its very light underside appearance, often almost without drawings, its long, wide wings and its flight style characterized by hovering and shaking , the species is usually relatively easy to determine even from greater distances. However, the determination is more difficult in the African winter quarters, where the Beaudouin short- toed eagle ( Circaetus beaudouini ) is a very similar species that was long considered a subspecies of C. gallicus . However, this is overall darker and clearly banded brown-gray on the underside. The under wing coverts are flaked cinnamon brown.
Short-toed eagles are gray-brown on top; Drawing features such as the lighter edges of the upper wing coverts can only be seen from close proximity. The arm wings are dark brown, the hand wings on the upper side almost black. In the upper view of the flying bird, these differences in color create a clear color contrast between the relatively light, white-speckled upper wing-coverts and the darker arm or almost black hand wings. The head looks very large when the eagle is sitting; the large, forward-facing eyes with yellow irises appear almost owl-like. This feature is not noticeable in flight. Short-toed eagles are usually very light on the underside. The under wing-coverts are indistinctly brownish spotted and zoned, the arm and hand wings are bordered in dark gray; the tips of the wings are gray-black. Often the throat and chest are clearly cinnamon brown in color, which can create a hood-like appearance, but this feature does not appear in all birds. The medium-long, rather narrow tail has an indistinct, triple, dark banding; from a greater distance, however, it appears almost without drawings. The belly, rump and trousers are mottled with very different intensities of light brown on a very light background. The greenish-gray legs are not feathered from the intertarsal joint, the claws are black.
The sexes hardly differ in color. The size dimorphism in favor of the females, which is common in birds of prey, is also very weak. However, females with a body weight of up to 2.3 kilograms are on average 20 percent heavier than males. The juvenile plumage is also very similar to that of the colored short-toed eagle. The only good distinguishing feature can be a bright, line-like drawing that separates the large cover feathers from the wings; this feature, which can only be seen from above, is no longer present in colored birds. Short-toed eagles fly with flat, very slow and powerful wing beats. Your flight movements appear delayed, almost as if in slow motion. They are often in a horizontal position of their wings in the wind and also shake frequently and persistently. When gliding, the wings in the wrist are strongly angled and stretched out.
voice
The male's calls are surprisingly melodious; remotely they are reminiscent of the flute of an oriole . The most common call is a two-syllable Kiiii-jo in which the first syllable is drawn out and strongly emphasized, the second syllable fades away full and short (audio sample). It can be heard above all when approaching the eyrie. The basic pattern of this call is varied depending on the situation and can be reminiscent of the calls of the black woodpecker and the osprey . At the eyrie itself, the male calls in mostly two-syllable sequences that have a bell-like or xylophone -like tone coloration. Particularly soft i-joa sounds are uttered near a partner and express particular familiarity. Females call less frequently and less resonantly in very similar phonetic patterns; Often you can hear both partners in a duet for minutes (audio sample).
distribution and habitat
The breeding areas of the short-toed eagle are mainly in the southern western and central Palearctic and on the Indian subcontinent . Only in north-eastern Europe do breeding occurrences of the species reach latitude 60 ° north. The short-toed eagle is isolated from this nowhere closed range in some regions of the Arabian Peninsula , in Inner Mongolia , as well as on some of the Lesser Sunda Islands . The short-toed eagles of the Lesser Sunda Islands have long been thought to be overwintering populations of Central Asia, but they are actually breeding occurrences of resident birds.
In the western and central Palearctic, the short-toed eagle occurs in the Maghreb states , on large parts of the Iberian Peninsula , parts of central and southern France, and eastwards across the Apennine Peninsula , the Balkan Peninsula , Asia Minor and parts of the Caucasus region to the Elburs and Zagros Mountains . Brood occurrences exist in Israel and, as far as known, much smaller ones, in Lebanon , Syria , Jordan and in the northern part of the Sinai Peninsula .
In Eastern and Northeastern Europe, the breeding occurrences are mainly in Belarus , the Ukraine and in the European part of Russia, from where the distribution area continues to Central Asia to the eastern edge of Lake Balkhash. The deposits that are furthest northward are in the Baltic States and in Russia north of Saint Petersburg .
Central Europe was always in the border area of the distribution area, only in northern Italy, Slovenia , Slovakia and Hungary there are small breeding occurrences.
In recent years, short-toed eagles have increased again in southern Switzerland ; In 2012 a pair of short-toed eagles brooded in Valais for the first time. From 2012 to 2017 there were eight breeding records in Switzerland, with two pairs each breeding in 2015, 2016 and 2017.
Observations of wandering short-toed eagles occur regularly in central and northern Central Europe, but rarely; A surprise was the sighting of a specimen on the Isles of Scilly in 1999 .
The most important prerequisite for a breeding occurrence of this species is a sufficient supply of reptiles, especially snakes, as well as individual trees for the nest. In large parts of its range, the species inhabits dry, heat-favored, only sparsely overgrown and rocky areas, such as Mediterranean maquis , garrigue and similar forms of vegetation, such as the Phrygana that is common in the east of the Mediterranean coast . Sunlit mountain slopes and terrain with strong relief are particularly favorable landscape structures. It also appears in loose pine and mixed deciduous forests, as long as there is open space for hunting, occasionally also in extensively used cultivated land. In the east of its distribution area it mainly populates isolated steppe areas with trees, in the north also denser forests and woody trees that accompany rivers, especially if they border on larger heather or moorland areas. In winter quarters the species appears in semi-arid areas such as dry and thorn bush savannas .
The breeding areas of the short-toed eagle range from sea level to heights of about 2000 meters, in some cases, as in Morocco and India, even a little higher.
The space requirement of the species is usually large. In a Spanish study, action areas with an average size of 36 square kilometers were found; a study in Italy found a similar size. Within the action area, an area of different sizes, but usually at least 2 kilometers in circumference, is vigorously defended against conspecifics; The minimum eaves distance is also in this distance range, only in extremely densely populated areas, such as the Dadia Forest in northeast Greece, were lower eaves distances measured.
hikes
The short-toed eagles of the Palearctic are mostly migratory birds, those of the Indian subcontinent and the Lesser Sunda Islands resident birds. Some eagles from southern Spain and north-west Africa also remain in the breeding area. The wintering areas lie in a relatively narrow belt in the Sahel region south of the Sahara and north of the equator from Senegal eastwards to Ethiopia . The short-toed eagles leave the breeding areas from the end of August; from mid-September there will be train concentrations near Gibraltar , on the Bosporus and in Israel. It is not known where the divide between East and West migrants lies. The northern Italian birds first migrate to the northwest and only turn southwest on the French Mediterranean coast; the central and southern Italians cross the Mediterranean at the narrow point between Sicily and Cap Bon . It is not known where Inner Mongolia's short-toed eagles winter. The return home takes place on the same routes, but on a broader front , so that there are no particular concentrations of trains at the known bottlenecks. The first eagles arrive in the breeding area as early as March, and their migration home is completed in mid-April.
An adult short-toed eagle with a transmitter covered the 4700 kilometers from its breeding area in France to the wintering area in Niger in 20 days; the longest daily distance was 467 kilometers.
Food and subsistence
The food of the short-toed eagle consists almost entirely of snakes . In addition, other reptiles, mammals and birds only play a subordinate role. Occasionally invertebrates such as snails and worms , and occasionally beetles and other large insects, are also eaten.
Among the snakes, the species prefers larger specimens with a length of about one meter, in India even specimens over 1.8 meters in length have been found as prey. Young animals are fed with correspondingly smaller animals. In Europe outweigh coluber , rat snakes, like the Äskulapnatter , arrow snake and leopard snake and lizards snakes and snakes swimming as grass snake and viper snakes in the range of prey. It catches smooth snakes and dice snakes less frequently, and otters such as adder or aspic viper are also less common among the prey animals. Apparently it prefers non-poisonous species, but it also preyes on poisonous snakes. In the forest of Dadia grass snakes made up almost half of the snakes captured, followed by lizard snakes. The European horned viper , which is not uncommon in the area , was probably not captured due to its small size. Nothing is known about the prey range of the Central Asian, Indian and Southeast Asian populations; There is also no detailed information about the prey animals in winter quarters.
In addition to this snake food that predominates quantitatively by far, are all available in the breeding area lizards including slow-worm and Sheltopusik beaten. In the Dadia Forest, in which 8 different lizards occur, only the two largest, the Scheltopusik and the Eastern Green Lizard , were found to be prey. Some species of geckos , turtles and small monitor lizards as well as amphibians such as frogs and toads are occasionally eaten. Small mammals such as mice , shrews , hamsters , rats and rabbits are part of the rare but regular prey, as well as various species of birds up to the size of jays and pigeons . However, many small mammals and amphibians that were found in the dump analyzes are likely to have been included with the snake prey.
The food requirement of an adult short-toed eagle is about 1–2 medium-sized snakes per day; the nestling needs up to 200 grams per day, which, extrapolated to the entire nestling time, corresponds to a number of up to 270 snakes with a total weight of around 11 kilograms.
The most commonly practiced hunting method is a slow hovering flight at altitudes between 150 and 400 meters, usually favored by thermals. Short-toed eagles frequently shake, and occasionally they hunt in a low, serpentine search flight. Hunting from high seat and on foot are also among the hunting strategies of this type. If a prey is spotted, the eagle falls like a parachute and grabs the snake immediately behind its head; often this is bitten off immediately. The prey is always devoured head first, either on the ground or in flight. Short-toed eagles transport their almost always dead prey to the eyrie exclusively in their beak.
Breeding biology
Pair formation and nest building
Short-toed eagles become sexually mature at the age of 3–4 years. They lead a largely monogamous, seasonal partnership; Reparations of last year's breeding partners are likely due to the very high degree of local loyalty of both sexes. Overall, the courtship is not very noticeable. Balzelement most essential is the garlands flight , which in a similar, but significantly expressive central characteristic even when Wespenbussard can be observed. The breeding partners or the male rise alone near the eyrie, drop about 15 meters and then with one or two wing beats to reach the previously lost height again; A bird often carries a snake in its beak, drops it and catches it again shortly afterwards, or passes it on to its partner. Persistent kiiii-jo calls can be heard during these flights .
Nest building begins very soon after arrival in the breeding area, in the Palearctic from mid-March, in the East Asian breeding areas after the end of the summer monsoon in early November. Both partners participate, but the male more intensely. The nest location is usually the top, more rarely the middle of the crown or a side branch of different, usually not particularly high trees, occasionally also bushes. Pine or oak are particularly often chosen as nest trees. Nests at heights over 10 meters are rather rare. Even in rock faces, the clumps are usually placed on bushes or stunted trees, only in exceptional cases directly on rock. Eyries are almost always rebuilt, old ones are rarely repaired or expanded or nests of other bird species are adapted. The eyrie is a rather small construction for the size of the species made of twigs and branches with an average diameter of 60 centimeters and a height of no more than 30 centimeters; clumps that are only used several times grow into larger structures. The shallow nest hollow is always covered with green twigs, often also with heather. Due to the average size of the nest, the head and thrust of breeding short-toed eagles often protrude beyond the edge of the nest and can therefore be seen from below.
Clutch, brood and rearing of the young bird
Egg-laying begins in the Maghreb at the beginning of the last decade of March; Fresh clutches can be found in the Palearctic until May; in India it begins in December and lasts until May. Short-toed eagles breed only once a year in the entire range; if the clutch is lost early, there is a subsequent clutch. The clutch always consists of only one relatively large, broadly elliptical, pure white egg with an average size of 74 × 58 millimeters and a weight of around 150 grams. The breeding season is very long at up to 47 days, as is the nestling season, the duration of which varies between 60 and 80 days depending on the weather and nutritional situation. Above all, it is the female that breeds and later takes over the huddling and cutting up the prey for the chick; it is only replaced a few times a day by the male who procures prey for chicks and females. When the nestling is four weeks old, the female also begins prey flights. Small chunks of meat are first presented to the chick, and it is only when it is around 2 weeks old that it begins to crop small snakes. At 3 weeks, a nestling is already able to devour a medium-sized snake 80 centimeters long and 4 centimeters thick. Often the nestling pulls the snake out of the throat of the adult bird bringing the food. In the Palearctic, most young eagles fly out between mid-July and mid-August; However, their parents will look after them for several weeks before they take their first turn.
Data on breeding success or reproduction numbers are sparse and are based only on small, unrepresentative studies. In various studies, the reproduction rate, i.e. the number of young eagles flown out per breeding pair and year, was between 0.3 and 0.86 individuals. The maximum age of a recovered ringed bird was 17 years.
Systematics
The short-toed eagle is one of five species in the genus Circaetus . It is the only species of this genus that is not only found in Africa. Observations of mixed broods with the Beaudouin short-toed eagle and the black-breasted short-toed eagle ( C. pectoralis ) led to the latter two species being united with C. gallicus and viewed as its subspecies. Since neither the frequency of these mixed broods nor the breeding success, let alone the fertility of possible offspring, are known, Ferguson-Lees considers a separation into three separate species within a superspecies to be appropriate.
Despite the very large area, which is fragmented into widely separated breeding areas, no subspecies of the short-toed eagle are recognized. In the past, the slightly smaller short-toed eagles of the Lesser Sunda Islands were assigned to a subspecies C. heptneri ; However, this assessment is currently not supported by the majority.
Stock situation
The stocks of the short-toed eagle decreased drastically from the middle of the 19th century; Direct tracking, tracking of prey and loss of habitat were decisive for this. The small Central European populations in Germany, Austria, Luxembourg , Switzerland and the Netherlands have expired in the last 100 years. Today the large populations in Southeastern and Eastern Europe as well as those of the Iberian Peninsula and France seem to remain largely constant in their numbers. Stock estimates for the non-European populations are not available.
The IUCN does not list the species at any risk level; Ferguson-Lees & Christie estimate the total world population at a maximum of 26,000 breeding pairs, of which about half are in the Western Palearctic.
In addition to habitat loss, direct persecution is still the most important cause that minimizes the population. Lots of short-toed eagles are shot down on the train in particular. Most of the 50 short-toed eagles that arrived in Malta in one day during the autumn migration in 1993 are documented.
literature
- Hans-Günther Bauer and Peter Berthold : The breeding birds of Central Europe. Existence and endangerment. Aula-Wiesbaden 1998 p. 94, ISBN 3-89104-613-8 .
- Mark Beaman and Steven Madge: Handbook of Bird Identification. Europe and Western Palearctic. Ulmer-Stuttgart 1998. pp. 187 and 230, ISBN 3-8001-3471-3 .
- James Ferguson and David A. Christie: Raptors of the World. Houghton Mifflin Company Boston, New York 2001. pp. 445-448; 126, ISBN 0-618-12762-3 .
- Dick Forsman: The Raptors of Europe and The Middle East. Christopher Helm London 2003. pp. 156-166; ISBN 0-7136-6515-7
- Urs N. Glutz von Blotzheim (Hrsg.): Handbook of the birds of Central Europe. Edit and a. by Kurt M. Bauer and Urs N. Glutz von Blotzheim. 17 vols. In 23 parts. Academ. Verlagsges., Frankfurt / M. 1966ff., Aula-Verlag, Wiesbaden 1985ff. (2nd ed.). Vol. 4 Falconiformes. Aula-Verlag, Wiesbaden 1989 (2nd edition). Pp. 274-295, ISBN 3-89104-460-7 .
- Theodor Mebs and Daniel Schmidt: The birds of prey in Europe, North Africa and the Middle East. Biology, characteristics, stocks. Franckh-Kosmos Verlag GmbH & Co. KG, Stuttgart 2006. pp. 331–339, ISBN 3-440-09585-1 .
Web links
- Circaetus gallicus onthe IUCN Red List of Threatened Species .
- Videos, photos and sound recordings of Circaetus gallicus in the Internet Bird Collection
- Age and gender characteristics (PDF; 3.3 MB) by J. Blasco-Zumeta and G.-M. Heinze (eng.)
- Short-toed eagle feathers
Individual evidence
- ^ Forsman (1999) p. 157
- ↑ Ferguson-Lees & Christie (2001) p. 446
- ^ Forsman (1999) p. 157
- ↑ Call1 (WAV) birdsongs.it. Retrieved October 21, 2019.
- ↑ Call3 (MP3) birdsongs.it. Retrieved October 21, 2019.
- ↑ Ferguson-Lees & Christie (2001) p. 446
- ↑ News from the Swiss Dispatch Agency (SDA) of December 27, 2012
- ↑ Claudia Müller: Rare and remarkable breeding birds 2017 in Switzerland. Der Ornithologische Beobachter 2018/115, H. 4., pp. 339-352
- ↑ Ferguson-Lees & Christie (2001) p. 446
- ↑ Mebs & Schmidt (2006) p. 154.
- ↑ Ferguson-Lees & Christie (2001) p. 446
- ↑ Mebs & Schmidt (2006) p. 155
- ↑ Mebs & Schmidt (2006) p. 155
- ↑ Bernd-U. Meyburg, Christiane Meyburg & Jean-Claude Barbraud: Migration Strategies of an Adult Short-Toed Eagle Circaetus gallicus Trecked by Satellite In: Alauda 66 (1), 1998: 39-48
- ↑ DE Bakaloudis, CG Vlachost and GJ Holloway: Habitat use by short-toed eagles Circaetus gallicus and their reptilian prey during the breeding season in Dadia Forest (north-eastern Greece) In: Journal of Applied Ecology 1998, 35, 821-828
- ↑ Ferguson-Lees & Christie (2001) p. 446
- ↑ DE Bakaloudis, CG Vlachost and GJ Holloway: Habitat use by short-toed eagles Circaetus gallicus and their reptilian prey during the breeding season in Dadia Forest (north-eastern Greece) In: Journal of Applied Ecology 1998, 35, 821-828
- ↑ DE Bakaloudis, CG Vlachost and GJ Holloway: Habitat use by short-toed eagles Circaetus gallicus and their reptilian prey during the breeding season in Dadia Forest (north-eastern Greece) In: Journal of Applied Ecology 1998, 35, 821-828
- ↑ HBV (1989) p. 294
- ↑ HBV (1989) p. 294
- ↑ HBV (1989) p. 287
- ↑ HBV (1989) p. 293
- ↑ Mebs & Schmidt (2006) p. 156
- ↑ Mebs & Schmidt (2006) p. 156
- ↑ Ferguson-Lees & Christie (2001) p. 448
- ↑ Bauer & Berthold (1998) p. 94
- ↑ Circaetus gallicus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- ↑ Ferguson-Lees & Christie (2001) p. 448
- ↑ Mebs & Schmid (2006) p. 153
- ↑ Ferguson-Lees & Christie (2001) p. 448
