The mistle thrush (Turdus viscivorus) is a bird common to much of Europe, temperate Asia and North Africa. It is a year-round resident in a large part of its range, but northern and eastern populations migrate south for the winter, often in small flocks. It is a large thrush with pale grey-brown upper parts, a greyish-white chin and throat, and black spots on its pale yellow and off-white under parts. The sexes are similar in plumage, and its three subspecies show only minimal differences. The male has a loud, far-carrying song which is delivered even in wet and windy weather, earning the bird the old name of stormcock. Historically, the name was also sometimes spelled "missel thrush".
Found in open woods, parks, hedges and cultivated land, the mistle thrush feeds on a wide variety of invertebrates, seeds and berries. Its preferred fruit include those of mistletoe, holly, rowan, and yew. Mistletoe is favoured where it is available, and this is reflected in the thrush's English and scientific names; the plant, a parasitic species, benefits from its seeds being excreted by the thrush onto branches where they can germinate. In winter, a mistle thrush will vigorously defend mistletoe clumps or other fruit-bearing trees as a food reserve for when times are hard, chasing off other thrushes and other fruit-eating birds like waxwings.
The open cup nest is built against a trunk or in a forked branch, and is fearlessly defended against potential predators, sometimes including humans or cats. The clutch, typically of three to five eggs, is incubated for 12–15 days, mainly by the female. The chicks fledge about 14–16 days after hatching. There are normally two broods. There was a range expansion in the 18th and early 19th centuries, and a small decline in recent decades, perhaps due to changes in agricultural practices. Given its numbers and large range, this thrush is classified by the International Union for Conservation of Nature as being of least concern.
Taxonomy The mistle thrush was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae under its current scientific name.Linnaeus (1758) p. 168. Turdus is the Latin for "thrush", and viscivorus, "mistletoe eater", comes from viscum "mistletoe" and vorare, "to devour".Jobling (2010) p. 393.Jobling (2010) p. 404. The bird's liking for mistletoe berries is also indicated by its English name, "mistle" being an old name for the plant.
There are more than 60 species of medium to large thrushes in the genus Turdus, characterised by rounded heads, longish pointed wings, and usually melodious songs.Clement et al. (2000) pp. 36–38. A mitochondrial DNA study identified the mistle thrush's closest relatives as the similarly plumaged song and Chinese thrushes; these three species are early offshoots from the Eurasian lineage of Turdus thrushes after they spread north from Africa. They are less closely related to other European thrush species such as the blackbird (T. merula) which are descended from ancestors that had colonised the Canary Islands from Africa and subsequently reached Europe from there.
At least eight subspecies have been proposed, but the differences between them are mainly clinal, with birds being paler and less densely spotted in the east of the range. The accepted subspecies as of 2024 are:Clement et al. (2000) pp. 397–491. T. v. viscivorus, named by Linnaeus, 1758, the nominate subspecies. Europe, and western Asia east to western Siberia and southeast to northern Iran. T. v. bonapartei, Cabanis, 1860. Central Asia, south to northern Pakistan, northwestern India, and western Nepal. T. v. deichleri, Erlanger, 1897. Northwest Africa, Corsica, Sardinia. There is some dispute as to the boundary between T. v. viscivorus and T. v. bonapartei; some cite birds from Siberia east of the Ob as being in T. v. bonapartei, while others restrict T. v. bonapartei to the populations further south in the mountains of central Asia, with the entire Siberian population in T. v. viscivorus. An isolated population in Crimea has sometimes been separated as T. v. tauricus, but this is not considered to be a valid form. Mistle thrush fossils have been found in Pleistocene deposits from Poland and Sicily.
Description
The mistle thrush is the largest thrush native to Europe. The nominate subspecies measures in length, with a wingspan. It weighs , with an average of around . It has a stocky upright posture when on the ground. It has pale grey-brown upperparts, the chin and throat are greyish-white, and the yellowish-buff breast and off-white belly are marked with round black spots. The spotting becomes denser on the lower chest. The long tail has white tips on the outer feathers, and the underwing coverts are white. The eyes are dark brown and the bill is blackish with a yellowish base to the lower mandible. The legs and feet are yellowish-brown. There are no plumage differences between the sexes. Juveniles are similar to adults, but they have paler upperparts with creamy 'teardrop' centres to many of the feathers and smaller spots on the yellowish underparts. By their first winter they are very similar to adults, but the underparts are usually more buff-toned.
There is clinal variation in nominate T. v. viscivorus across its range with the darkest birds in western Europe, and the palest in Siberia and Turkey. The southeastern subspecies T. v. bonapartei is in length, and therefore slightly larger than the nominate form. It is paler grey above and whiter below, with fewer black spots. The southwestern subspecies T. v. deichleri resembles T. v. bonapartei in appearance, but is closer in size to the nominate T. v. viscivorus, although it has a more slender bill.
Adults have a full moult after breeding, beginning between late May and the end of June, and completed by early October. Juvenile birds have a partial moult, replacing their head, body, and covert feathers; this is completed by October, although the start of the moult depends on when the chicks hatched.
The mistle thrush is much larger, paler and longer-tailed than the sympatric song thrush. In the western Himalayas it could be confused with both the plain-backed and the long-tailed thrushes. These are similar to the mistle thrush, but the plain–backed thrush lacks obvious wing bars, is more rufous above than its relative, and is barred rather than spotted below. The long-tailed thrush has olive-toned upperparts, bars on its breast and two wing bars. Juvenile mistle thrushes are superficially similar to White's thrush, but that species has golden-yellow plumage, scalloped underparts and a distinctive underwing pattern.
Voice The male mistle thrush has a loud melodious song with fluted whistles, sounding like chewee-trewuu ... trureetruuruu or similar, repeated three to six times, and used to advertise his territory, attract a mate and maintain the pair bond.Clement et al. (2000) p. 41. The tone resembles that of the song thrush or blackbird, but compared to its relatives the mistle thrush's repertoire is less varied and the delivery is slower. The song is, however, much louder, often audible up to 2 km (2,000 yd) away. The song is given from a treetop or other elevated position mainly from November to early June. The male is most vocal in the early morning, and its tendency to sing after, and sometimes during, wet and windy weather led to the old name "stormcock". The song may be heard in any month, although it is uncommon from July to August while the thrush is moulting. The main call, given by both sexes, is a dry chattering krrrr, louder when it is alarmed or excited. It is often likened to the sound of a football rattle, a form of musical ratchet. There is also a squeaky tuk contact call.
Distribution and habitat
The mistle thrush breeds in much of Europe and temperate Asia, although it is absent from the treeless far north, and its range becomes discontinuous in southeast Europe, Turkey and the Middle East. In these warmer southern areas, it tends to be found in the milder uplands and coastal regions.
The mistle thrush is a partial migrant: birds from the north and east of the range wintering in the milder areas of Europe and North Africa. Scandinavian and Russian birds start moving south from mid-September onwards, most birds wintering in Europe, western Turkey and the Middle East. Between mid-October and November, large numbers cross the Strait of Gibraltar and others pass through Cyprus, but there is hardly any migration across the North Sea. Breeding birds in the British Isles and north-west Europe are resident or move only short distances. In the Himalayas, the breeding population moves to nearby lower-altitude sites in winter. Return migration starts mainly from late March, although it can be a month earlier in the Middle East, and northern breeders may not arrive back on their territories until late April or early May. Migration may be by day or night, and typically involves individuals or small groups. Vagrant birds have occurred in the Azores, China, Crete, Faroe Islands, Iceland, Japan, Oman, Saudi Arabia, Sikkim and the United Arab Emirates. In the winter 2017/2018 the first record of a mistle thrush in North America was at Miramichi in New Brunswick, found on 9 December 2017 and remaining until 24 March 2018.
The mistle thrush is found in a wide range of habitats containing trees, including forests, plantations, hedges and town parks. In the south and east of its range, it inhabits upland coniferous woodland and the range extends above the main tree line where dwarf juniper is present. Breeding occurs at up to in the mountains of North Africa, and occasionally much higher, to . In the highlands of Europe, its preferred altitude is from .Snow & Perrins (1998) pp. 1230–1234. More open habitats, such as agricultural land, moors and grassy hills, are extensively used in winter or on migration.
There is evidence that this species has changed its natural habitat in at least parts of its range. In Germany and elsewhere in central Europe, it was found only in coniferous forest until the mid-1920s when its range rapidly expanded, first into farmland, and then to suburbs and urban parks. The reasons for this expansion are unclear.Fuller (2003) p. 28. In areas of intensive farming, such as eastern England, arable land has in turn largely been abandoned in favour of built-up areas with their greater variety of green habitats.
Behaviour Mistle thrushes are found as individuals or pairs for much of the year, although families forage together in late summer, and groups may merge to form large flocks when food sources are plentiful. It is not uncommon for up to 50 thrushes to feed together at that time of year. They roost at night in trees or bushes, again typically as individuals or pairs, except in late summer or autumn when families may roost together.
The mistle thrush is quite terrestrial, hopping with its head held up and body erect; when excited, it will flick its wings and tail. The flight consists of undulating bounds interspersed with glides.
Breeding
Mistle thrushes breed in the year subsequent to their hatching; they are monogamous and stay as a pair throughout the year in areas where they are not migratory. Their territories are much larger than those of blackbirds or song thrushes; although the nest territory is only about , around is used for feeding. Territories are normally reoccupied in subsequent years. Territories are larger in woods than in farmland. The male will attack intruders into its breeding area, including birds of prey and corvids, and sometimes cats or humans. Courtship feeding of the female by her partner has sometimes been observed.