Western jackdaw

thumb|Adult C. m. monedula, Vaxholm, Sweden

The western jackdaw (Coloeus monedula), also known as the Eurasian jackdaw, the European jackdaw, or simply the jackdaw, is a passerine bird in the crow family. It is found across Europe, western Asia and western North Africa; it is mostly resident, although northern and eastern populations migrate south in the winter. Four subspecies are recognised, which differ mainly in the darker or paler greyscale of the plumage on the head and nape. Linnaeus first described it formally, giving it the name Corvus monedula. The common name derives from the word jack, denoting "small", and daw, a less common synonym for "jackdaw", and the native English name for the bird.

Measuring in length, the western jackdaw is a black-plumaged bird with a grey nape and distinctive pale iris. It is gregarious and vocal, living in small groups with a complex social structure in farmland, open woodland, on coastal cliffs, and in urban settings. Like its relatives, jackdaws are intelligent birds, and have been observed using tools. An omnivorous and opportunistic feeder, it eats a wide variety of plant material and invertebrates, as well as food waste from urban areas. Western jackdaws are monogamous and build simple nests of sticks in cavities in trees, cliffs, or buildings. About five pale blue or mint green eggs with brown to grey speckles are laid and incubated by the female. The young fledge in four to five weeks.

Systematics

Etymology

The western jackdaw was one of the many species originally described by Carl Linnaeus in his 18th century work Systema Naturae. Owing to its supposed fondness for picking up coins, Linnaeus gave it the binomial name Corvus monedula, choosing the specific name mǒnēdŭla, which is derived from moneta, the Latin stem of the word "money". Jackdaws are now placed in the genus Coloeus, from the Ancient Greek κολοιός (koloios) for jackdaw, while most older works retained the two jackdaw species in Corvus.

The original Old English words ċēo and ċeahhe (pronounced with initial ch) gave modern English "chough"; Chaucer sometimes used this word to refer to the western jackdaw, This onomatopoeic name, based on the western jackdaw's call, now refers to corvids of the genus Pyrrhocorax; the red-billed chough (Pyrrhocorax pyrrhocorax), formerly particularly common in Cornwall, became known initially as the "Cornish chough" and then just the "chough", the name transferring from one species to the other.

The common name jackdaw first appeared in the 16th century, and is thought to be a compound of the forename Jack, used in animal names to signify a small form (e.g. jack snipe), and the archaic native English word daw. Formerly, western jackdaws were simply called "daws". The jack part of the common name is again likely of onomatopoeic origin from the metallic chyak call, but this is not supported by the Oxford English Dictionary. Daw, first used for the bird in the 15th century, is held by the Oxford English Dictionary to be derived from the postulated Old English dawe, with cognates in Old High German tāha, Middle High German tāhe or tāchele, and modern German Dahle or Dohle, and dialectal Tach, Dähi, Däche and Dacha; it is likewise of onomatopoeic origin, based on another of the commonest calls the bird makes.

An archaic collective noun for a group of jackdaws is a "clattering". Another name for a flock is a "train".

Taxonomy

A study in 2000 found that the genetic distance between western jackdaws and the other members of Corvus was greater than that within the rest of the genus. This led Pamela Rasmussen to reinstate the genus name Coloeus, created by Johann Kaup in 1829, in her Birds of South Asia (2005), a treatment also used in a 1982 systematic list in German by Hans Edmund Wolters. A study of corvid phylogeny undertaken in 2007 compared DNA sequences in the mitochondrial control region of several corvids. It found that the western jackdaw, and the closely related Daurian jackdaw (C. dauuricus) of eastern Russia and China, were basal to the core Corvus clade. The two species of jackdaw have been reported to hybridise in the Altai Mountains, southern Siberia, and Mongolia. Analysis of the mitochondrial DNA of specimens of the two species from their core ranges show them to be genetically distinct.

Subspecies

thumb|right|C. m. monedula in Sweden. This subspecies has a whitish partial collar.

There are four recognised subspecies of the western jackdaw. C. m. monedula intergrades into C. m. soemmerringii in a transition zone running from Finland south across the Baltic and eastern Poland to Romania and Croatia.

The Nordic jackdaw (C. m. monedula) (Linnaeus, 1758), the nominate subspecies, is found in eastern Europe. Its range extends across Scandinavia, from southern Finland south to Esbjerg and Haderslev in Denmark, through eastern Germany and Poland, and south across eastern central Europe to the Carpathian Mountains and northwestern Romania, Vojvodina in northern Serbia, and Slovenia. It breeds in south-eastern Norway, southern Sweden, and northern and eastern Denmark, with occasional wintering in England and France. It has been recorded as a rare vagrant to Spain. It has a pale nape and sides of the neck, a dark throat, and a light grey partial collar of variable extent. It is darker in colour than the other subspecies and lacks the whitish border at the base of the grey nape. Its subspecific name was given in honour of the German anatomist Samuel Thomas von Sömmerring. It is distinguished by the nape and the sides of the neck being paler, creating a contrasting black crown and lighter grey part collar. Most of the plumage is a shiny black, with a purple (in subspecies monedula and spermologus) or blue (in subspecies cirtensis and soemmerringii) sheen on the crown, forehead, and secondaries, and a green-blue sheen on the throat, primaries, and tail. The cheeks, nape and neck are light grey to greyish-silver, and the underparts are slate-grey. The legs are black, as is the short stout bill, though the head and neck plumage of male birds fades more with age and wear, particularly just before moulting. Western jackdaws undergo a complete moult from June to September in the western parts of their range, and a month later in the east. On the ground, western jackdaws have an upright posture and strut briskly, their short legs giving them a rapid gait. They feed with their heads held down or horizontally. Flying western jackdaws are distinguishable from other corvids by their smaller size, faster and deeper wingbeats and proportionately narrower and less fingered wing tips. They also have shorter, thicker necks, much shorter bills and frequently fly in tighter flocks. They can be distinguished from choughs by their uniformly grey underwings and their black beaks and legs. The western jackdaw is very similar in morphology, behaviour, and calls to the Daurian jackdaw, with which its range overlaps in western Asia. Adults are readily distinguished, since the Daurian has a pied plumage, but immature birds are much more similar, both species having dark plumage and dark eyes. The Daurian tends to be darker, with a less contrasting nape than the Western.

Vocalisations

thumb|Western jackdaw calling in flight on [[Inisheer, Ireland]]

Western jackdaws are voluble birds. The main call, frequently given in flight, is a metallic and squeaky chyak-chyak or kak-kak. Perched birds often chatter together, and before settling for the night, large roosting flocks make a cackling noise. Western jackdaws also have a hoarse, drawn-out alarm call, From day 25, the young cease calling and become silent if they hear an unfamiliar noise.

Distribution and habitat

The western jackdaw is found from Northwest Africa through all of Europe, except for the subarctic north, and eastwards through central Asia to the eastern Himalayas and Lake Baikal. To the east, it occurs throughout Turkey, the Caucasus, Iran, Iraq, Afghanistan, Pakistan, and northwestern India. Censuses of bird populations in marginal uplands in Great Britain show that western jackdaws greatly increased in numbers between the 1970s and 2010, although this increase may be related to recovery from previous periods when they were regarded as pests. The UK population was estimated at 2.5 million individuals in 1998, up from 780,000 in 1970.

thumb|A western jackdaw on [[Inisheer, Ireland]]

Most populations are resident, but the northern and eastern populations are more migratory, Their range expands northwards into Russia to Siberia during summer and retracts in winter. In Syria, they are winter vagrants and rare residents with some confirmed breeding taking place. The subspecies soemmerringii occurs in south-central Siberia and extreme northwestern China and is accidental to Hokkaido, Japan. A small number of western jackdaws reached northeastern North America in the 1980s and have been found from Atlantic Canada to Pennsylvania. They have also occurred as vagrants in Gibraltar, Mauritania, and Saint Pierre and Miquelon, The same data from Warsaw, collected from 1977 to 2003, showed that the wintering western jackdaw population had increased four-fold. The cause of the increase is unknown, but a reduction in the number of rooks may have benefited the species locally, or rooks overwintering in Belarus may have caused western jackdaws to relocate to Warsaw.

Fossil record

Fossils of the western jackdaw are known from the Late Pleistocene, specifically MIS 3 of the Iberian Range, in a fossil assemblage believed to represent an accumulation of bones made by diurnal birds-of-prey.

Behaviour

left|thumb|A family group in [[Bushy Park, London.]]

thumb|A western jackdaw in flight.

Generally wary of people in the forest or countryside, western jackdaws are much tamer in urban areas. Flocks increase in size in autumn and birds congregate at dusk for communal roosting, Western jackdaws frequently congregate with hooded crows Western jackdaws sometimes mob and drive off larger birds such as European magpies, common ravens, or Egyptian vultures (Neophron percnopterus); one gives an alarm call which alerts its conspecifics to gather and attack as a group. Occasionally, a sick or injured western jackdaw is mobbed until it is killed. Young males establish their individual status before pairing with females. Upon pairing, the female assumes the same social position as her partner. Unmated females are the lowest members in the pecking order, and are the last to have access to food and shelter. In the defensive-threat posture, the bird lowers its head and bill, spreads its tail and ruffles its feathers. Supplanting is where one bird moves in and displaces another from a perch-site. The second bird usually retreats without resorting to a fight. Western jackdaws fight by launching themselves at each other feet-first and then wrestling with their feet intertwined and pecking at each other. Other individuals gather and call noisily.

Western jackdaws entreat their partners to preen them by showing their nape and ruffling their head feathers. Birds mainly preen each other's head and neck. Known as allopreening, this behaviour is almost always done between birds of a mated pair. Some pairs do separate in the first few months, but almost all pairings of over six months' duration are lifelong, ending only when a partner dies. Widowed or separated birds fare badly, often being ousted from nests or territories and unable to rear broods alone.

Nest platforms can attain a great size. A mated pair usually constructs a nest by improving a crevice by dropping sticks into it; it is then built on top of the platform formed. This behaviour has led to the blocking of chimneys and even resulted in nests crashing down into fireplaces, sometimes with birds still on them.

In his The Natural History of Selborne, Gilbert White notes that western jackdaws used to nest in crevices beneath the lintels of Stonehenge, and describes an example of the bird using a rabbit burrow for nesting. They can take over old nest sites of the black woodpecker (Dryocopus martius) and stock dove (Columba oenas). The eggs are a lighter colour than those of other corvids, being smooth, a glossy pale blue or blue-green with darker speckles ranging from dark brown to olive or grey-violet. Egg size and weight varies slightly between subspecies; those of subspecies monedula average and in weight, those of subspecies soemmerringii in size and in weight, and those of subspecies spermologus in size and in weight. The eggs are incubated by the female for 17–18 days until hatching as naked altricial chicks, which are completely dependent on the adults for food. They fledge after 28–35 days, Replacement clutches are very rarely laid in the event of clutch failure. Nest robbers include the common raven in Spain, tawny owl, and least weasel (Mustela nivalis) in England, and brown rat (Rattus norvegicus) in Finland. The European pine marten (Martes martes) raids isolated nests in Sweden but is less successful when nests are part of a colony.

The western jackdaw tends to feed on small invertebrates up to in length that are found above ground, including various species of beetle (particularly cockchafers of the genus Melolontha, and weevil larvae and pupae.), Diptera, and Lepidoptera species, as well as snails and spiders. Also eaten are small rodents, bats, the eggs and chicks of birds, and carrion such as roadkill. Vegetable items consumed include farm grains (barley, wheat and oats), weed seeds, elderberries, acorns, and various cultivated fruits. The diet averages 84% plant material except when breeding, when the main food source is insects.

Opportunistic and highly adaptable, the western jackdaw varies its diet markedly depending on available food sources. They have been recorded taking eggs and nestlings from the nests of the skylark (Alauda arvensis), Manx shearwater (Puffinus puffinus), razorbill (Alca torda), common guillemot (Uria aalge), grey heron (Ardea cinerea), and Eurasian collared dove (Streptopelia decaocto). The saker falcon (Falco cherrug) has been reported stealing food from western jackdaws on powerlines in Vojvodina in Serbia.

Western jackdaws practice active food sharing – where the initiative for the transfer lies with the donor – with a number of individuals, regardless of sex or kinship. They also share more of a preferred food than a less preferred food. The active giving of food by most birds is found mainly in the context of parental care and courtship. Western jackdaws show much higher levels of active giving than has been documented for other species, including chimpanzees. The function of this behaviour is not fully understood, though it has been found to be detached from nutrition and compatible with hypotheses of mutualism, reciprocity and harassment avoidance. It has also been proposed that food sharing may be motivated by prestige enhancement.

Parasites and diseases

Western jackdaws have learned to peck open the foil caps of milk bottles left on the doorsteps after delivery by the milkman. The bacterium Campylobacter jejuni has been isolated from their beaks and cloacae so milk can become contaminated as they drink. This activity was linked to cases of Campylobacter gastroenteritis in Gateshead in northeast England and led the Department of Health to suggest that milk from bottles which had been pecked open should be discarded. It was recommended that steps be taken to prevent birds from pecking bottles open in the future.

An outbreak of a gastrointestinal illness in Spain which was causing mortalities in humans has been linked to western jackdaws. During a post-mortem on an affected bird, a polyomavirus was isolated from the spleen. The illness appeared to be a co-infection of this with Salmonella and the virus has been provisionally named the crow polyomavirus (CPyV). Segmented filamentous bacteria have been isolated from the small intestine of a western jackdaw, although their pathogenicity or role is unknown.

Pest control

The western jackdaw has been hunted as a pest, though not as heavily culled as other species of corvid. After a series of poor harvests in the early 1500s, Henry VIII of England| introduced a Vermin Act in 1532 "ordeyned to dystroye Choughes (i.e. jackdaws), Crowes and Rokes" to protect grain crops from their predations. Western jackdaws were notorious for their fondness for fruit, especially cherries. This act was adopted piecemeal, but Elizabeth I of England| passed the Act for the Preservation of Grayne in 1566 which was enforced more vigorously. The species was hunted for threatening grain crops and for propensity for nesting in belfries until the mid-20th century. Particularly large numbers were culled in the county of Norfolk. Western jackdaws were also culled on game estates for raiding the nests of other birds for eggs. In a 2003 dissertation on public opinion of corvids, Antonia Hereth notes that the German naturalist Alfred Brehm considered the western jackdaw to be a lovable bird, and did not attribute any negative impacts of to this species with regard to agriculture.

The western jackdaw is one of a very small number of birds that can legally be used as decoys or trapped in cages in the United Kingdom. The other pest species that can be controlled by trapping are the crow, jay, magpie and rook. An authorised person does not need to prove that the birds were a nuisance before trapping them, but must comply with the provisions of the Wildlife and Countryside Act 1981. As of 2003, the western jackdaw was listed as a potential species for targeted hunting in the European Union Birds Directive, and hunting has been encouraged by German hunting associations.]]

thumb|upright|A jackdaw pictured in the [[coat of arms of the Sauvo municipality]]

An ancient Greek and Roman adage runs "The swans will sing when the jackdaws are silent", meaning that wise or educated people will only speak once the foolish have become quiet. In Ancient Greek folklore, a jackdaw can be caught with a dish of oil. A narcissistic creature, it falls in while looking at its own reflection. The mythical Princess Arne Sithonis was bribed with gold by King Minos of Crete, and was punished by the gods for her greed by being transformed into an equally avaricious jackdaw, who still seeks shiny things. The Roman poet Ovid described jackdaws as harbingers of rain in his poetic work Amores. Pliny notes how the Thessalians, Illyrians, and Lemnians cherished jackdaws for destroying grasshoppers' eggs. The Veneti are fabled to have bribed the jackdaws to spare their crops. Czech superstition formerly held that if jackdaws are seen quarreling, war will follow, and that jackdaws will not build nests at Sázava after being banished by Saint Procopius. Nineteenth century belief in the Fens held that seeing a jackdaw on the way to a wedding was a good omen for a bride.

The jackdaw is featured on the Ukrainian town of Halych's ancient coat of arms, the town's name allegedly being derived from the East Slavic word for the bird. In The Book of Laughter and Forgetting (1979), Milan Kundera notes that Franz Kafka's father Hermann had a sign in front of his shop with a jackdaw painted next to his name, since "kavka" means jackdaw in Czech.<!-- Three jackdaws are featured on the Trzy Kawki coat of arms, used by several szlachta (noble) families under the Polish-Lithuanian Commonwealth.

It is the symbolic bird of Southwest Finland.-->

Alex K Halych 2.svg|Coat of arms of the Principality of Halych

Recueil_d'armoiries_polonaises_-_COA_of_Halych_Land_crop2.png|Coat of arms of Halych Land

Alex_K_Grundwald_flags_1410-07.svg|Flag of Halych land at the Battle of Grunwald 1410

Coat of Arms of Ivano-Frankivsk Oblast.svg|Coat of arms of Ivano-Frankivsk Oblast