Jackdaw ( Coloeus monedula )
|( Linnaeus , 1758)|
The Jackdaw ( Coloeus monedula , Syn. : Corvus monedula ) is a Singvogelart from the family of corvids (Corvidae). It is one of two species in the genus of jackdaws ( Coloeus ). Compared to the closely related species of ravens and crows ( Corvus ), it is a rather small representative of the corvids. It is characterized by black and gray plumage, a stocky beak and light blue eyes. The distribution area of the jackdaw extends from the North African Atlas Mountains over Europe to Lake Baikal . It prefers open habitats with trees, rocks or old buildings as habitats. The jackdaw's diet consists mainly of seeds and insects , but it also eats carrion or human waste on occasion . Jackdaws usually live in larger groups and form lifelong monogamous pairs. They build their nests in holes and niches of all kinds, for example in woodpecker holes or building niches. The female incubates four to six eggs, the nestlings are then fed by both parents.
First described the jackdaw was 1758 in Linnaeus' Systema Naturae . It is divided into four subspecies and is the sister species of the East Asian Magpie Jackdaw ( Coloeus dauuricus ). The jackdaw is considered harmless worldwide, the population is probably in the double-digit million range. In some regions of Europe, however, it is declining mainly due to a lack of nesting sites.
Build and color
The jackdaw is a medium-sized raven bird, 33–39 cm in length. It looks - especially in comparison with most ravens and crows - stocky and has a stocky, powerful beak and relatively short legs. The tail of the jackdaw is medium-long and slightly rounded in comparison to the species, its wings are round, weakly fingered and, when put on, fall back slightly behind the tail. Male jackdaws are on average larger than females, even if there is an overlap in the dimensions: males reach a wing length of 208–255 mm and a tail length of 122–138 mm. Its beak is 20.6–21.5 mm long from the nostrils to the tip, the male barrel bone measures 42.3–49.0 mm. The male weight is 174-300 g. With 205–250 mm wing length, 115–134 mm tail length, a 19.8–23.2 mm long beak and 41.2–46.5 mm barrel length and a weight of 175–282 g, females only achieve insignificantly smaller maximum dimensions, but significantly smaller mean values.
The jackdaw shows a certain variation in plumage across its range and also within the postulated subspecies. However, all birds have the same basic pattern. The sexes are very similarly colored and differ at most in a slightly lighter coloring of male birds at certain times of the year. The nasal bristles , forehead, front part of the head, eye area, cheeks and the chin down to the throat are black in adult jackdaws. The black headstock shimmers metallic blue or purple. The back part of the head, the back of the head, the nape and the ear covers contrast with the black part due to their light to slate gray color, but merge into black in the cheek, throat and neck area. On the sides of the neck and in the nape of the neck, in some individuals, a sometimes more, sometimes less clear, silver-gray band forms, which widens towards the chest and separates the plumage of the head from the plumage. The back of the jackdaw, like the wings and tail, is black-gray to black. The wing feathers shimmer weakly green or bluish. The underside of the jackdaw's body - chest, flanks, abdomen, and abdomen - are slate gray and darker than the back of the head. From moult to moult, especially the gray areas of the plumage fade. With black feathers, usually only the edges fade, which results in a scaly pattern on the back. The nasal bristles turn rusty brown over time. Adult birds have a white-blue iris , which stands out clearly from the black feathering of the face. Their beak is black, as are their legs.
Juveniles differ in color from their adult conspecifics only in a few details. Their plumage colors are duller and have significantly less sheen than that of adult birds. The black parts of the plumage of adult birds appear browner or greyish, and the color delimitation of the head plate from the back of the head is less clear. The most obvious difference is the color of the eyes: after the juvenile moult, the iris color of the birds changes from light blue to dark brown. Only after about a year does it get lighter from the outside, from the age of three it is completely white-blue again.
Flight image and locomotion
On the ground, the jackdaw moves with a brisk, brisk gait. Due to its small size and shorter legs, it appears more hectic when walking than larger species of its genus. She always carries her head high, the tail is slightly angled up. The jackdaw runs or hops over the ground less often, sometimes with the help of the wings. In rough terrain or in the branches it moves hopping. Jackdaws are able to hold onto short protrusions or depressions in the rock or from walls even on vertical walls, using their tail as a support.
The jackdaw is also noticeable in flight because of its liveliness and agility. It flies with rapid, quite jerky wing beats and reaches comparatively high speeds. So it is h faster than 60 km / carrion crows ( Corvus corone ) or rooks ( Corvus frugilegus ), but adjusts its speed in mixed shoals. Due to its relatively low weight and its more compact construction, the jackdaw is also more manoeuvrable than larger corvids, which gives it an advantage in terms of food sources. Unlike heavier crows, it can run on thin branches and land and take off faster than it does. Updrafts uses the Jackdaw for acrobatic-looking flight maneuvers and effortless sailing.
Jackdaws are call-happy birds and have - probably due to their high degree of sociality - a very broad repertoire of sounds. Short, monosyllabic and metallic-clicking calls that sound higher than the vocalizations of larger ravens or crows are characteristic of the species. Kja , kjä and chack are the jackdaw calls that are heard most frequently and exist in many different variants.
The jackdaw has many situation-specific calls, most of which are choppy and high-pitched. In addition, she also lets you hear drawn out, croaking vocalizations, such as an errrr or ärrrr in a state of excitement . The mating season sing jackdaws with a variety of a variety shouts composite Subsong who were freed from their proper context. Through the stronger emphasis on individual calls, a certain mood can also be expressed in a sub-song. Imitation of ambient noises or calls from other species is not known from jackdaws in the wild.
Spreading and migrations
Art area and distribution history
The distribution area of the jackdaw covers almost the entire temperate western Palearctic from Central Asia to North Africa. The breeding areas have an area of 15.6 million km², the species area is around 20.0 million km² in size. The easternmost breeding areas are on Lake Baikal . From there they extend westward along the 12 ° C July isothermal to the coast of the White Sea . Further west, the breeding areas extend to Finland , Sweden and Norway . The Fennoscandian breeding population largely spares the northern inland and the Atlantic coast and is concentrated around the Baltic Sea , but the jackdaw is absent on the northern coast of the Bottenwiek . Almost all of mainland Europe is settled south of Scandinavia , the jackdaw is missing here - due to the colder summer climate - only in the high mountains, on the Biscay and on the Portuguese west coast. She populates the larger British Isles across the board, only the highlands and more remote archipelagos do not belong to the breeding areas. With the exception of the Balearic Islands and Corsica , the jackdaw can also be found as a breeding bird on the large islands of the Mediterranean . In North Africa, the occurrences - primarily due to the climate - are smaller and more disjoint than in Eurasia . In Morocco , the jackdaw occurs only in two areas in the Atlas Mountains , which also extend into the lowlands east of Ouezzane . In Algeria the breeding area includes the northwest coast and Constantine , earlier occurrences in Tunisia are extinct. The jackdaw colonizes Asia Minor almost everywhere, a smaller occurrence exists in northern Israel . To the east, the Caucasus and northwestern Iran belong to the breeding areas. Central Asia is only populated along the outer regions and in the northwest to the Aral Sea . An isolated population exists in the eastern Elbursgebirge . The breeding area in the east includes the high mountains on the edge of the Tibetan plateau to the Mongolian highlands . In Kashmir there is another small breeding population on the southwestern edge of the Himalayas .
The early and middle Pleistocene finds attributed to the jackdaw come mainly from southern and southeastern Europe and are limited to regions with a warm climate or warmer interglacials . It was not until the end of the Pleistocene that fossils were found in northern Central Europe. Jon Fjeldså assumes that after the Ice Ages the jackdaw made its way north and west from heat islands along the Mediterranean and Black Seas and from Turkestan . Before humans reached the Balearic Islands, the jackdaw was also native there. The north of Europe, on the other hand, was settled late, in today's Denmark and Norway the jackdaw was probably only introduced around 1000 BC Chr. Breeding bird. In the 19th and 20th centuries, the art area expanded significantly. First, the jackdaw pushed north along the Gulf of Bothnia , which was probably favored by a warming of the local climate and increasing urbanization of the species. In Tunisia, on the other hand, the existing breeding resources died out towards the end of the 19th century, while the jackdaw disappeared in Malta through intensive hunting . In Siberia , the species was able to develop new regions by opening up the taiga forests until 1980 . More recently, it has expanded its area to the north in the British Isles.
Although jackdaws can be found year-round in much of the range, most populations leave their breeding areas in winter. Because migrating breeding populations are replaced by winter guests, the migration is often not noticed. The migration routes to the winter quarters run mostly in a westerly direction on the Atlantic coast and the adjacent seas, and in a south-westerly direction in continental Eurasia. Breeding populations to the north move farther than more southerly: the Central Asian Russian populations cover up to 700 km, the Eastern European populations only slightly more than 300 km, while Swiss birds often only migrate a few kilometers. The number of resident birds also varies from northeast to southwest. Around 70% of Polish but only 23% of Belgian jackdaws leave the breeding areas in winter. In North Africa all breeding populations consist of resident birds , but they are reinforced in winter by fewer birds that migrate across the Mediterranean. Turkish birds use Mesopotamia as winter quarters, jackdaws from Central Asia can be found in Pakistan and Afghanistan in winter . In winter, resident birds also leave the higher elevations and move into the lowlands. Many populations then concentrate on human settlements, where there is sufficient sleeping space and food sources. In parts of Northern Europe, jackdaws do not even move out of the cities when the circumstances are favorable. The migration continues in the north one in September, in the south it can be moved to November. Withdrawal begins early in February and March and is usually completed by the end of March.
The range of potential nesting sites and suitable areas for foraging influence the habitat choice of the jackdaw. As a predominant cave breeder , it is heavily dependent on old wood stocks with woodpecker holes, rock holes or buildings with sufficient niches in their habitat, at least during the breeding season . Quarries , rocky coasts, settlements with old buildings, medieval churches as well as parks and woods with large, old trees are therefore often breeding habitats used by the jackdaw. They also serve as a place to sleep outside of the breeding season. Forests are only populated in the edge area (maximum 2 km from the edge of the forest). As part of the Church Tower Habitat campaign , the German Nature Conservation Union is trying to preserve existing nesting facilities in church towers for jackdaws, kestrels and barn owls and to create new ones.
The species needs relatively spacious, open spaces to forage on the ground. These areas must have low vegetation (maximum 15–20 cm) so that the jackdaw can move on them, therefore parking areas and pastureland are preferred . Because they should also be insect-rich , the jackdaw likes to use dry grass and extensively farmed areas . In field studies outside of the breeding season, the foraging grounds were 0.5–3.1 km away from the roosts, during the breeding season they were 0.4–2.4 km away from the nest. In the course of the year the jackdaw uses very different areas - pastureland, steppes , stubble fields , flood plains - for foraging.
The jackdaw is relatively weather and temperature tolerant, but avoids extremes of heat and cold. It is more likely to be found in the lowlands and valleys than in mountainous areas. It is usually widespread below 500 m; between 500 and 1000 m it is often only found in local collections. In some exceptional cases, the breeding habitats extend beyond 1000 m, for example in the Alps , in the Atlas or in Kashmir up to around 2000 m. Outside the breeding season, it can also be found in altitudes of up to 3500 m.
Way of life
Like other ravens and crows, the jackdaw is omnivorous . The main focus of the food spectrum is on seeds and insects. It also eats small vertebrates , snails , bird eggs , carrion and, in settlements, human waste.
In a UK study, plant seeds were eaten all year round. In autumn it was mostly beans , peas and the seeds of fleshy fruits, in winter legumes also dominated the vegetable diet. While invertebrates were largely absent from winter food, they gained in importance from spring to autumn in particular, and beetles , two-winged birds and caterpillars were eaten particularly often . Other European studies have found similar distributions. The jackdaw eats carrion less than other ravens and crows. Locally, otherwise insignificant food sources can be used heavily if they are sufficiently available and the resident jackdaws have developed corresponding traditions. For example, some urban populations mainly feed on clutches of Turkish pigeons ( Streptopelia decaocto ), although eggs make up only a marginal part of the diet elsewhere. On cattle pastures, the jackdaw eats not only the soil insects but also the ectoparasites of the grazing animals. While plant foods play an important role in fledgling birds, they are usually completely absent from the diet of nestlings. Their parents feed them almost exclusively protein-rich animal food, especially insects.
The jackdaw mainly takes up its food on the ground in open areas. Most of the time, the food is simply picked up from the surface, or objects such as stones or pieces of wood are turned over in order to reach insects living underneath. Unlike long-billed crows, they rarely dig. Jackdaws can be very adept at catching flying insects from the air or picking fruit from branches. Collected food is hidden as with all corvids. This hiding instinct is rather weak in the jackdaw, it hides excess food less often and more superficially than other corvids. Indigestible food components are choked up as bulges , but usually avoided when eating.
Social and learning behavior
The jackdaw is a very social raven bird. If there are enough nesting places, it forms breeding colonies in which double-digit numbers of breeding pairs often breed close together and tolerate each other. Usually only the nest niche and the immediate vicinity are defended against conspecifics. Outside the breeding grounds, jackdaws often move in larger groups, for example when foraging. Usually these associations and the relationships between the individuals are rather loose, but their core is usually jackdaws who know each other from a common breeding colony. The group formation primarily has a protective function, because the individual jackdaw has to invest less time in controlling the environment and swarms can assert themselves against larger carrion crows . During the breeding season, mostly non-breeding groups can be found in the groups of 20–50 birds. After the breeding season, young birds and breeding pairs are added, which means that the group size can grow to 200 jackdaws. It is not uncommon for jackdaws to be found in mixed groups with rooks , which they like to join during the migration to the summer and winter quarters or to the sleeping places. Several hundred to 1,000 jackdaws can usually be found together at shared sleeping places, but there have also been reports of sleeping colonies of 10,000 or more individuals.
The question of whether there are hierarchies within jackdaw groups has not been completely clarified. At least within breeding colonies, the dominance of individual pairs over others is interpreted as a hierarchy in disputes. However , this dominance is far less pronounced in fielding squads; all in all, the dominance relationships in groups also appear to be extremely dynamic. There can be very close personal relationships between individuals, but they do not have to be sexually motivated. Brood partners show no individual distance . They often lapse into synchronous behavior , their close bond is expressed in gestures of affection such as scratching and stroking their bills. Away from settlements, jackdaws are usually shy of people, but they hardly show fear where they are not persecuted. Jackdaws are more self-confident in flocks than alone, and they often only venture out of cover when foreign birds or socially inferior conspecifics have survived a situation unscathed. Jackdaws only learn many connections through trial and error . They are able to form analogies or to differentiate between superficially similar test setups, for example in dot pattern and metronome tests.
Reproduction and breeding
Jackdaws usually reach sexual maturity at the age of two years, and less often after one year. They form monogamous and, as a rule, lifelong breeding communities. In the first six months of a pair relationship, new pairings can often occur, after which the relationship is usually stable. The search for nesting sites usually begins towards the end of winter. Jackdaw pairs vigorously defend their nesting sites against their conspecifics, even if they later give them up and choose others. By the beginning of May, all nesting sites are usually occupied. Rock holes, woodpecker caves , but also abandoned rabbits , chimneys, wall openings or hollow metal structures serve as such . Particularly narrow passages or niches that are difficult to reach are preferred. The settlement density in urban areas can reach 4.4–9.9 pairs per km², while in rural areas it is only 0.06 pairs on average. The nest consists of a substructure of twigs as thick as a finger, usually 30 cm long, which are often simply thrown into the brood cavity until they get caught and form a platform. The nest cavity is then lined with various soft materials, such as moss, paper, fur or dung . Both partners take part in building the nest, sometimes they get help from one-year-old brood helpers , who leave the nest as soon as the eggs are laid.
The eggs are laid from April to May. The clutch consists of two to eight, usually between four and six bluish eggs, which are speckled dark. The mean clutch size in the entire range is always around five eggs. The female incubates them for 16-20 days, during which it is fed by the male. The nestlings fledge after 28-41 days, the length of time depending on the food supply and the size of the clutch. After they leave, the young jackdaws are dependent on their parents for about five weeks. The breeding success in late breeding pairs is less than in early breeders. Usually no more than one or two boys in a clutch fledge. Smaller clutches with two to four eggs produce the most young relatively, in clutches of five eggs absolutely most nestlings fledge. The fifth and further eggs are the least likely to hatch. If they do, they almost never fledge.
Life expectancy, diseases and causes of mortality
The most important predators fledged Jackdaws are the goshawk ( Accipiter gentilis ), the peregrine falcon ( Falco peregrinus ) and the stone ( Martes foina ) and the pine marten ( M. martes ). In addition to the two species of marten, the mouse weasel ( Mustela nivalis ) and the tawny owl ( Strix aluco ) are the greatest threats to nestlings . Cold weather with a simultaneous lack of insects is extremely critical for nestlings and regularly leads to high death rates. Common parasites are featherlings such as the host-specific Corvonirmus varius varius and Menacanthus monedulae , mites of the order Astigmata ( e.g. Montesauria cylindrica ) and the hedgehog tick ( Ixodes hexagonus ). In addition, the jackdaw is also host to species of suckers , tapeworms and nematodes , which are also known from other birds.
Birds that have just fledged have the highest mortality; according to various estimates, it is between 30 and 56% of the offspring in the first year of life. Adult birds have a 30-40% mortality rate and a life expectancy of two years and seven months after the first year. According to a long-term study of the age structure of jackdaw populations, wild jackdaws over 13 years of age are rare and make up less than 1% of the population. The highest documented age of a wild jackdaw is 20 years and four months for a bird from Sweden, further record values are over 19 years. Jackdaws can get older in captivity, so two males lived in London Zoo for 29 and 28 years respectively.
Systematics and history of development
Like almost all other animals known in Europe in the middle of the 18th century, the jackdaw was first described in Carl von Linnés Systema Naturæ in 1758 , at that time under the name Corvus monedula . The specific epithet monedula is an old Latin name for the jackdaw. It can already be found in Cicero and Ovid and is probably derived from the widespread superstition that the jackdaw would prefer to steal gold coins ( Latin moneta for mint) and other valuables.
There is a close relationship to the comparatively long-billed ravens and crows ( Corvus ). Together with the very similar East Asian Elster Dohle ( Coloeus dauuricus ) it forms the genus Coloeus . DNA studies classify both species as sister groups of ravens and crows. The relationship between the two jackdaw species as sister species was also confirmed. The examined gene sequences of jackdaw and magpie jackdaw differed by 5.8%. In the molecular clock scheme , this indicates a separation a little less than three million years ago. This period coincides with the beginning of the Pleistocene , when the onset of Ice Ages separated the populations of many Eurasian species. Despite the rather large genetic distance, magpie jackdaw and jackdaw hybridize in eastern Central Asia, where their breeding areas overlap.
Based on the plumage drawing, the jackdaw was divided into different subspecies early on . The consideration of even minor differences - such as the width of the neck ring or the glossy color of the crown - led to more than ten different subspecies being described, which showed smooth transitions to others and were limited to small-scale regions. Most of these subspecies were not recognized, but the phenotypic classification was retained. Today four subspecies are usually listed:
- Subspecies restricted to the Algerian Constantine . A light, almost uniformly slate-gray shape with a weakly pronounced neck ring and little contrast in the plumage. It is named after the Roman city of Cirta , the forerunner of today's Constantine.
- Coloeus monedula monedula Linnaeus , 1758 :
- Nominate form from Scandinavia. A relatively light shape with a mostly clear neck ring.
- Coloeus monedula soemmeringi Fischer , 1811 :
- Subspecies from Eastern Europe from Finland, Eastern Germany and Greece to Asia. Rather light form with mostly pronounced neck ring. The epithet honors Samuel Thomas von Soemmerring .
- Coloeus monedula spermologus ( Vieillot , 1817) :
- Subspecies of western Europe from Denmark via western Germany, France and the Iberian Peninsula to Morocco. Relatively dark shape without a stripe on the neck, darker towards the southwest. The word spermologus is derived from the ancient Greek σπερμολόγος / spermologos for "semen eater".
This classification of the subspecies proved to be problematic several times in the past because it was difficult to differentiate. Deviations from the expected plumage patterns and flowing transitions across the distribution area were mostly interpreted as signs of mixed populations or isolated hybridization. However, an analysis of the DNA of various individuals from across the range came to the conclusion that members of putative subspecies were often less closely related to one another than to birds of other subspecies. The phenotypic differences would therefore not have a population-genetic cause, but would be of an individual nature. Whether the jackdaw is monotypic , i.e. has no genetically distinguishable subspecies, cannot yet be determined because the sample of the study was very small and did not include any cirtensis individuals.
Inventory and status
Knowledge of the existence of the jackdaw is poor. The figures obtained are largely based on estimates, which is why they vary widely. The Turkey and Russia accommodate each with 1-10 million breeding pairs most of the global stock of Dohle, Bulgaria follows with 1-5 million pairs. There are larger populations with around 600,000 breeding pairs on the British Isles , around 500,000 on the Iberian Peninsula and in Belarus with around 400,000 breeding pairs. Overall, depending on the geographical definition, Europe has 5–15 million breeding pairs and 16–45 million individuals. Extrapolated to the entire range, this results in a population of 21–90 million adult birds, according to BirdLife International .
BirdLife International classifies the species as Least Concern on this basis . However, the subspecies cirtensis is considered threatened in Algeria because many traditional breeding grounds have been lost due to the construction of dams. While the populations in Scandinavia, the British Isles, the Netherlands and Siberia increased through colonization of new habitats at the end of the 20th century, they thinned out in large parts of Europe. This shrinkage is mainly due to the demolition and renovation of old buildings, in which the jackdaw found sufficient breeding niches. In addition, the species suffers from measures to repel pigeons , which affect them just like the street pigeon . In rural areas she is particularly concerned about the decline in permanent green areas and the felling of old wood. As a countermeasure, conservationists are calling for greater consideration to be given to the jackdaw when renovating old buildings. In addition, nest boxes suitable for the jackdaw are hung up. These measures are accompanied by public relations work for the jackdaw in many European countries, for example BirdLife Austria , the Nature Conservation Union Germany (NABU) and the State Association for Bird Protection in Bavaria have named the jackdaw Bird of the Year 2012 to draw attention to their situation .
The German name of the Jackdaw can be restored to the Old High German Taha traced, probably an onomatopoeic name, which derived from the calls of birds. In Middle and Early New High German it changed to tāhe . In addition, since the 13th century , subsidiary forms with -l- ( talle , tole , dole ) can be identified, especially in Central Germany , from which the term “jackdaw”, which is used today in High German, developed.
As a widespread species and cultural follower, the jackdaw soon became the subject of broad cultural reception. The ancient Greeks , for example, emphasized their sociability and bond with couples in the saying “ a jackdaw always has a jackdaw ”, analogous to “like and like to join”. In his fable The Jackdaw and the Peacocks, Aesop made her appear as a deceiver who sneaks under the peacocks disguised with strange feathers. The negative portrayal of the jackdaw continued in later times, so it was already considered thieving by the Romans. This belief was also widespread in the Middle Ages and far into modern times. For example, the Silesian legend, The Schweidnitzer Councilor, written down by the Brothers Grimm , tells of a fraudulent city councilor who steals gold coins from the city treasury with a trained jackdaw. The jackdaw's loquacity has often been interpreted as conspiratorial whispering, and in the early modern period jackdaws in Britain were also seen as companions and assistants to witches .
Although the jackdaw tended to be viewed negatively, it was subject to relatively weak persecution. Probably their small size, more melodious cries, and fondness for plant foods prevented them from evoking the same dislike as the carrion crow , raven, or rook. Of all the species in the genus, the jackdaw was the least hunted in Europe, apart from regional exceptions such as Malta . Perhaps that is why she is now comparatively fearless towards humans.
Jackdaws are intelligent birds, which is why they used to be kept as pets . Especially when they already live with humans as a young bird, they can become very tame. However, keeping wild birds such as jackdaws is no longer permitted. Besides, it's not that simple. They are very energetic and will die if caged. As they get older, they often form a kind of couple bond with their caregiver and no longer pay attention to the rest of the family. They can even be jealous and aggressive towards other people.
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- Jackdaw feathers
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