Shale hawk
| Shale hawk | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Male shale hawk |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Falco concolor | ||||||||||||
| Temminck , 1825 |
The slate falcon ( Falco concolor ) is a member of the genus Falcon ( Falco ), the size of a kestrel, within the subfamily of the real falcon (Falconinae). In appearance it is very similar to representatives of the dark morphs of the somewhat larger Eleanor's falcon , with which the obligatory farmer also shares the wintering places on Madagascar . Slate hawks have largely synchronized their breeding season with the migratory peaks of small Palearctic migratory birds, on which they feed themselves and their young during their breeding season. Their widely dispersed breeding colonies are mainly located on cliffs in the central and eastern Sahara , on islands in the Red Sea and on the Arabian Peninsula .
For a long time, the IUCN assessed the slate falcon as not endangered ( least concern ). It has been on the list of potentially endangered bird species since 2008, as observations in the wintering areas have shown that the number of falcons has decreased significantly. Instead of the 100,000 individuals that were previously assumed, it is assumed that there are currently a maximum of 20,000 sexually mature individuals.
features
With a size of 32 to 37 and a wingspan of 75 to 88 centimeters, it is slightly smaller than the Eleanor's falcon and slightly larger than the tree falcon . In the adult dress, slate falcons of both sexes are colored blue-gray; Females are a little darker, so that the color contrast of the entire upper side plumage, which is recognizable in the male, to the almost blackish hand wings is hardly noticeable in them. In some individuals the cheeks, throat, and neck are somewhat lighter; a streak of beard is clearly evident in these. The featherless areas around the eyes and the wax skin are bright yellow-orange in the male and bluish in the female; These differences also form the only reliable basis for a field ornithological sex determination, since the reverse sex dimorphism in relation to size and mass in the Eleanor's falcon, as in all falcons, is only indistinctly pronounced. The legs are yellowish in both sexes, the nails black.
Birds up to their second autumn plumage differ significantly from adults. Apart from the smaller size, they strongly resemble female Eleonorian falcons of the light morph. Its upper side is gray-brown with significantly lighter feather edges. The underside on a creamy yellow or isabel-colored ground clearly dark with vertical lines. The top of the head is dark gray, the cheeks yellowish; a streak of beard is usually clearly visible. The feathered areas around the eyes and the wax skin are blue-gray. Slate falcons are colored by about 18 months.
In flight, shale falcons appear relatively large-headed and extremely long-winged, with the slender, pointed arm wings being particularly noticeable. In many shale hawks, the central control feathers of the overall short tail are somewhat elongated.
voice
The species is acoustically very present in the breeding colonies, especially in the later afternoon and evening. The most frequent call is a kii..kii..kii that is not ranked particularly quickly . In addition, a high-pitched , loud Krii-e. . kriie that reminds of the calls of the kestrel in many different ways.
distribution and habitat
The breeding distribution of the slate falcon is only partially known. It breeds in the central and south-eastern Sahara region of Libya , in north, central and eastern Egypt , in Israel , Jordan and Syria , in scattered colonies along the west and east coast of the Arabian Peninsula, and on rocky islands in the Red Sea. The southernmost breeding occurrences are in the Dahlak archipelago belonging to Eritrea , the easternmost on islands in the Persian Gulf and on the coast of Makran in Pakistan .
Slate falcons breed in arid, largely vegetation-free areas. Their breeding sites and breeding colonies are located on rocky cliffs, along cliffs or on coral islands, where they often set up their nesting sites under mangroves or in spring stocks . The breeding sites are very far in some areas, often several 100 meters, even up to a few kilometers apart; If there is little space but cheap food supply, such as on the breeding islands in the southern Red Sea, the nest spacing can be less than 10 meters.
During the breeding season, shale hawks are mostly found in low-lying areas and in coastal areas. In winter quarters they can be found up to an altitude of 1500 meters.
The territoriality of the species seems to depend heavily on the average food supply. For example, no territorially motivated aggression was found in an Israeli population that feeds mainly on migrating small birds, while slate falcons that breed on an island off the coast of Oman claimed a coastline of around 70 meters each.
hikes
Slate hawks are usually obligatory farmer migrants with wintering areas mainly in Madagascar and coastal areas in Mozambique . Occasional winter observations of slate falcons in the southernmost distribution areas suggest that some individuals may have overwintered in the breeding area. The migration does not begin until mid-October, but shale hawks can still be found on the breeding islands in the Red Sea in mid-November. The main migration route follows the course of the Nile and the Great Rift Valley . Western populations fly over the Gulf of Aden in a south-westerly direction in order to encounter the main train route. The winter quarters are reached towards the end of November; The move home will start at the end of February at the earliest. The arrival at the breeding sites takes place from the end of April, but mainly in May.
Food and subsistence
In terms of food acquisition, the species resembles the Eleonor's falcon. During the breeding season, shale hawks feed themselves and their offspring exclusively on birds, mainly small songbirds that migrate through the area. The largest prey are the hoopoes and the flying grouse , but the main prey is made up of smaller birds such as warblers , stranglers and sailors . The frequency of the different species in the shale falcon's diet varies both regionally and seasonally. In the early migration period palearctic early migrants like playing oriole or bee-eater an important role regionally are also often petrels captured.
Outside the breeding season, various large insects, such as grasshoppers , crickets , dragonflies and beetles, form the most important food components. Bats, lizards and small mammals are also beaten. Birds play a rather subordinate role during this time.
Breeding biology
Slate falcons become sexually mature towards the end of their first year of life; some females breed successfully in the first autumn following their birth, but mostly male and female first brooders are one year older. Nothing is known about courtship behavior and the duration of the couple bond. Sightseeing flights during the flight home could indicate that some slate falcons reach the breeding grounds already mated or at least mated.
The nesting site is on a level spot in a rock niche, in half caves on rocky cliffs, on the flat coral islands in the Red Sea also on the ground, if possible shaded by bushes or springs. North-facing locations are preferred in the rock breeding grounds. Slate falcons breed in dense colonies with a nesting site spacing of a few meters, but also in loose associations, in which the distance to the neighboring nest can be a few kilometers. Occasionally, crow's nests, especially those of the desert raven ( Corvus ruficollis ), are used as nesting sites. The nesting trough is scraped out a little, occasionally also sparsely covered with twigs. The main breeding season is synchronized with the main regional migration of songbirds; the laying time is between mid-July and mid-August. The clutch consists of 2 to 3 (1 to 4) eggs, which on average measure 40 x 31 millimeters and weigh 22 grams. They are incubated for around 28 days, mainly by the female, who is supplied with food by the male during this time. The young are also only eaten by the female with the food brought by the male. Excess prey is occasionally deposited in cool places. The nestling period lasts between 32 and 38 days. After about three weeks of leadership, the boys are self-employed. Nothing is known about juvenile dismigration, but observations of ringed falcons show a very high degree of loyalty to the breeding site.
Systematics
Despite the brood distribution fragmented into partially isolated colonies, no subspecies are distinguished. Genetic analyzes confirmed the close relationship of the species to the tree falcon and the Eleanor's falcon, which was suspected on the basis of morphological and behavioral similarities. With these, the slate falcon forms the monophyletic subgenus Hypotriorchis within the Falconinae. The extent to which other falcons such as the African tree falcon ( Falco cuvieri ) or the Malay tree falcon ( Falco serverus ) should be included in this group is still the subject of research.
Inventory and inventory development
Due to the large distribution area and the widely scattered and mostly inaccessible breeding sites, no detailed population figures are available. Around 1000 pairs breed at the known breeding sites, but only recently have colonies with quite a few individuals been discovered in Israel and Jordan. It is believed that many colonies have so far gone undetected. In the wintering areas, the shale hawk is about 10 times more common than the Eleanor's falcon, which based on the latest population figures of the Eleanor's falcon would correspond to a total population of at least 100,000 breeding pairs. Birdlife international assumes a world population of around 100,000 individuals; However, these estimates are still based on an old inventory of the Eleanor's falcon that has since become obsolete. The population of the slate falcon is currently not endangered.
literature
- Mark Beaman and Steven Madge: Handbook of Bird Identification. Europe and Western Palearctic. Stuttgart 1998, pp. 209 and 248, ISBN 3-8001-3471-3
- Data sheet Birdlife international (2007)
- James Ferguson-Lees , David A. Christie: Raptors of the World. Boston / New York 2001, ISBN 0-618-12762-3 , pp. 872-872-875; Plate 100 (p. 277).
- Dick Forsman: The Raptors of Europe and the Middle East . Helm London 1999. pp. 485-491. ISBN 0-7136-6515-7
- Benny Génsbøl and Walther Thiede: Birds of Prey. All European species, identifiers, flight images, biology, distribution, endangerment, population development. Munich 2005, ISBN 3-405-16641-1
- Theodor Mebs and Daniel Schmidt: The birds of prey in Europe, North Africa and the Middle East. Biology, characteristics, stocks. Stuttgart 2006, pp. 409-414, ISBN 3-440-09585-1
- Michael Wink, I. Seibold, F. Lotfikhah and W. Bednarek: Molecular systematics of holarctic raptors (Order Falconiformes) . In: Chancellor, RD, Meyburg, B.-U. & Ferrero, JJ (Eds.): Holarctic Birds of Prey. 29-48. (1998) Adenex & WWGBP.
swell
- ↑ BirdLife Factsheet on the Slate Falcon , accessed on August 5, 2011
- ↑ Ferguson-Lees & Christie (2001) p. 872
- ↑ Forsman (2003) pp. 489-490
- ^ Forsman (2003) p. 486
- ↑ Mebs & Schmidt (2006) p. 410
- ↑ Mebs & Schmidt (2006) p. 411
- ↑ Mebs & Schmidt (2006) p. 411
- ↑ Ferguson-Lees & Christie (2001) p. 872
- ↑ Ferguson-Lees & Christie p. 874
- ↑ Mebs & Schmidt (2006) p. 413
- ↑ Wink & Seibold et al. (1998)
- ↑ Mebs & Schmidt (2006) p. 410
- ↑ Data sheet Birdlife international
Web links
- Falco concolor in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Recordings from the great outdoors at www.fokus-natur.de