Western jackdaw
The western jackdaw, 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 colouration 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-grey irises. 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 blue-green eggs with brown 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 sometimes placed in the genus Coloeus, from the Ancient Greek κολοιός for jackdaw, though most subsequent works have retained the two jackdaw species in Corvus.The original Old English words ċēo and ċeahhe gave modern English "chough"; Chaucer sometimes used this word to refer to the western jackdaw, as did Shakespeare in Hamlet although there has been debate about which species he was referring to. This onomatopoeic name, based on the western jackdaw's call, now refers to corvids of the genus Pyrrhocorax; the red-billed chough, 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, and the archaic native English word daw. Formerly, western jackdaws were simply called "daws". The metallic chyak call may be the origin of the jack part of the common name, 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, citing the 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.
Names in English dialects are numerous. Scottish and north English dialects have included ka or kae since the 14th century. The Midlands form of this word was co or coo. Caddow is potentially a compound of ka and dow, a variant of daw. Other dialectal or obsolete names include caddesse, cawdaw, caddy, chauk, college-bird, jackerdaw, jacko, ka-wattie, chimney-sweep bird, and sea-crow. It was also frequently known quasi-nominally as Jack.
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, 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 of eastern Russia and China, were basal to the core Corvus clade. The names Coloeus monedula and Coloeus dauuricus have since been adopted by the International Ornithological Congress in their official list. 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
There are four recognized subspecies of the western jackdaw. All European subspecies intergrade where their populations meet. 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 , 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.
- The Western Eurasian jackdaw occurs in western, central and southern Europe and North Africa, from the British Isles, the Netherlands and the Rhineland in the north, through western Switzerland into Italy in the southeast, and the Iberian peninsula and Morocco in the south. It winters in the Canary Islands and Corsica. The name "spermologus" comes from the Greek σπερμολόγος, a picker of seeds. It is darker in colour than the other subspecies and lacks the whitish border at the base of the grey nape.
- The Eastern Eurasian jackdaw is found in northeastern Europe and northern and central Asia from the former Soviet Union to Lake Baikal and northwestern Mongolia and south to Turkey, Israel and the eastern Himalayas. Its southwestern limits are Serbia and southern Romania. It winters in Iran and northern India. Johann Fischer von Waldheim described this taxon as Corvus soemmerringii in 1811, noting its differences from populations in western Europe. 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.
- The Algerian jackdaw is found in Morocco and Algeria in Northwest Africa. It was also formerly found in Tunisia. The name "cirtensis" refers to the ancient city of Cirta in Numidia. The plumage is duller and more uniformly dark grey than the other subspecies, with the paler nape less distinct.
Description
Immature birds have duller and less demarcated plumage. The head is a sooty black, sometimes with a faint greenish sheen and brown feather bases visible; the back and side of the neck are dark grey and the underparts greyish or sooty black. The tail has narrower feathers and a greenish sheen.
There is very little geographic variation in size. The main differences are the presence or absence of a partial whitish collar at the base of the nape and variations in the colour of the nape and the tone of the underparts. Central Asian populations have slightly larger wings, while western populations have slightly heavier bills. Body colour becomes darker in mountain regions and humid climates further north, and paler elsewhere. However, individual variation, particularly in juveniles and during the months before moulting, can often exceed geographic differences.
The western jackdaw is a skilled flyer that can manoeuvre tightly, tumble and glide. It has distinctive jerky wingbeats when flying, though these are not apparent during migration. Wind tunnel experiments show that the preferred gliding speed is between per second and that the wingspan decreases as the bird flies faster. 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.
Within its range, the western jackdaw is unmistakable; its short bill and grey nape are distinguishing features. From a distance, it can be confused with a rook, or when in flight, with a pigeon or chough. 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.