The
Song Thrush (
Turdus philomelos) is a
thrush that breeds across much of
Eurasia. It is also known in
English dialects as
throstle or
mavis. It has brown upperparts and black-spotted cream or buff underparts and has three recognised
subspecies. Its distinctive
song, which has repeated musical phrases, has frequently been referred to in poetry.
The Song Thrush breeds in
forests, gardens and parks, and is partially
migratory with many birds wintering in southern
Europe,
North Africa and the
Middle East; it has also been introduced into
New Zealand and
Australia. Although it is not threatened globally, there have been serious population declines in parts of Europe, possibly due to changes in farming practices.
The Song Thrush builds a neat mud-lined
cup nest in a bush or tree and lays four or five dark-spotted blue
eggs. It is
omnivorous and has the habit of using a favourite stone as an "anvil" on which to smash
snails. Like other perching birds (
passerines), it is affected by external and internal
parasites and is vulnerable to predation by
cats and
birds of prey.
[edit]Taxonomy
The Song Thrush was described by
German ornithologist Christian Ludwig Brehm in 1831, and still bears its original
scientific name,
Turdus philomelos.
[2] The generic name,
Turdus, is the
Latin for
thrush, and the specific epithet refers to a character in
Greek mythology,
Philomela, who had her tongue cut out, but was changed into a singing bird. Her name is derived from the
Ancient Greek Φιλο philo- (
loving), and
μέλος melos(
song).
[3] The dialect names
throstle and
mavis both mean
thrush, being related to the
German drossel and
French mauvis respectively.
[4] Throstledates back to at least the fourteenth century and was used by
Chaucer in the
Parliament of Fowls.
[5] Mavis is derived via
Middle English mavys and
Old French mauvis from
Middle Breton milhuyt meaning "thrush."
[6] Mavis (Μαβής) can also mean "
purple" in
Greek.
[7]
[edit]Classification
A parent feeding chicks in their nest in a New Zealand garden
A recent molecular study indicates that the Song Thrush's closest relatives are the similarly plumaged
Mistle Thrush (
T. viscivorus) and the
Chinese Thrush (
T. mupinensis); these three species are early offshoots from the lineage of
Turdus thrushes before they diversified and spread across the globe, and hence are less closely related to other European thrush species such as the
Blackbird (
T. merula).
[8]
T. p. clarkei, described by German
zoologist Ernst Hartert in 1909, and named for Eagle Clarke, breeds in the rest of
Great Britain and
Ireland and on mainland
Europe in France,
Belgium, the
Netherlands and possibly somewhat further east. It has brown upperparts which are warmer in tone than those of the nominate form, an olive-tinged rump and rich yellow background colour to the underparts. It is a partial migrant with some birds wintering in southern France and
Iberia. This form
intergrades with the nominate subspecies in central Europe, and with
T. p. hebridensis in the
Inner Hebrides and western
Scotland, and in these areas birds show intermediate characteristics.
[9] Additional subspecies, such as
T. p. nataliae of
Siberia, proposed by the
Russian Sergei Buturlin in 1929, are not widely accepted.
[9]
[edit]Description
The Song Thrush (as represented by the nominate subspecies
T. p. philomelos) is 20 to 23.5 centimetres (8 to 9.25 in) in length and weighs 50–107
grammes (1.8 to 3.8
oz). The sexes are similar, with plain brown backs and neatly black-spotted cream or yellow-buff underparts, becoming paler on the belly. The underwing is warm yellow, the bill is yellowish and the legs and feet are pink. The upperparts of this species become colder in tone from west to east across the breeding range from
Sweden to Siberia. The juvenile resembles the adult, but has buff or orange streaks on the back and wing
coverts.
[9]
The most similar European thrush species is the
Redwing (
T. iliacus), but that bird has a strong white
supercilium, red flanks, and shows a red underwing in flight. The
Mistle Thrush (
T. viscivorus) is much larger and has white tail corners, and the
Chinese Thrush (
T. mupinensis), although much more similar in plumage, has black face markings and does not overlap in range.
[9]
The Song Thrush has a short, sharp
tsip call, replaced on migration by a thin high
seep, similar to the Redwing's call but shorter. The alarm call is a
chook-chook becoming shorter and more strident with increasing danger. The male's song, given from trees, rooftops or other elevated perches, is a loud clear run of musical phrases, repeated two to four times,
filip filip filip codidio codidio quitquiquit tittit tittit tereret tereret tereret, and interspersed with grating notes and mimicry. It is given mainly from February to June by the Outer Hebridean race, but from November to July by the more widespread subspecies.
[9] For its weight, this species has one of the loudest bird calls.
[10]
An individual male may have a repertoire of more than 100 phrases,
[11] many copied from its parents and neighbouring birds. Mimicry may include the imitation of man-made items like telephones,
[12] and the Song Thrush will also repeat the calls of captive birds, including exotics such as the
White-faced Whistling Duck.
[9]
[edit]Distribution and habitat
Birds of the nominate subspecies were introduced to New Zealand and Australia by
acclimatisation societiesbetween 1860 and 1880, apparently for purely sentimental reasons.
[13] In New Zealand, where it was introduced on both the main islands, the Song Thrush quickly established itself and spread to surrounding islands such as the
Kermadecs,
Chatham and
Auckland Islands.
[14] Although it is common and widespread in New Zealand, in Australia only a small population survives around
Melbourne.
[15] In New Zealand, there appears to be a limited detrimental effect on some invertebrates due to predation by introduced bird species,
[16] and the Song Thrush also damages commercial fruit crops in that country.
[17] As an introduced species it has no legal protection in New Zealand, and can be killed at any time.
[18]
Juvenile song thrush in forest understory near Dombaih, Russia (Caucasus Mountains)
The Song Thrush typically nests in forest with good undergrowth and nearby more open areas, and in western Europe also uses gardens and parks. It breeds up to the tree-line, reaching 2,200 metres (7,250 ft) in
Switzerland. The island subspecies
T. p. hebridensis breeds in more open country, including
heathland, and in the east of the Song Thrush's Eurasian range, the nominate subspecies is restricted to the edge of the dense conifer forests.
[9]
In intensively farmed areas where agricultural practices appear to have made cropped land unsuitable, gardens are an important breeding habitat. In one
English study, only 3.5% of territories were found in farmland, whereas gardens held 71.5% of the territories, despite that habitat making up only 2% of the total area. The remaining nests were in woodlands (1% of total area).
[19]
The winter habitat is similar to that used for breeding, except that high ground and other exposed localities are avoided;
[20] however, the island subspecies
T. p. hebridensis will frequent the seashore in winter.
[9]
[edit]Behaviour
Breaking the shell of a snail
The Song Thrush is not usually gregarious, although several birds may roost together in winter or be loosely associated in suitable feeding habitats, perhaps with other thrushes such as the Blackbird,
Fieldfare, Redwing and
Dark-throated Thrush.
[9] Unlike the more nomadic Fieldfare and Redwing, the Song Thrush tends to return regularly to the same wintering areas.
[20]
This is a
monogamous territorial species, and in areas where it is fully migratory, the male re-establishes its breeding territory and starts singing as soon as he returns. In the milder areas where some birds stay year round, the resident male remains in his breeding territory, singing intermittently, but the female may establish a separate individual wintering range until pair formation begins in the early spring.
[20]
During migration, the Song Thrush travels mainly at night with a strong and direct flight action. It flies in loose flocks which cross the sea on a broad front rather than concentrating at short crossings (as occurs in the migration of large soaring birds), and calls frequently to maintain contact.
[9] Migration may start as early as late August in the most easterly and northerly parts of the range, but the majority of birds, with shorter distances to cover, head south from September to mid-December. However, hard weather may force further movement. Return migration varies between mid-February around the Mediterranean to May in northern Sweden and central Siberia.
[9] Vagrants have been recorded in
Greenland, various Atlantic islands, and West Africa.
[9]
[edit]Breeding and survival
The female Song Thrush builds a neat cup-shaped nest lined with mud and dry grass in a bush, tree or creeper, or, in the case of the Hebridean subspecies, on the ground. She lays four or five bright glossy blue
eggs which are lightly spotted with black or purple;
[9] they are typically 2.7 x 2.0 centimetres (0.79 x 1.06 in) in size and weigh 6.0 grammes (0.21 oz), of which 6% is shell.
[3] The female incubates the eggs alone for 10–17 days, and after hatching a similar time elapses until the young fledge. Two or three broods in a year is normal, although only one may be raised in the north of the range.
[9] On average, 54.6% of British juveniles survive the first year of life, and the adult annual survival rate is 62.2%. The typical lifespan is three years, but the maximum recorded age is 10 years 8 months.
[3] The Song Thrush is occasionally a host of
parasitic cuckoos, such as the
Common Cuckoo, but this is very rare because the thrush recognizes the cuckoo's
non-mimetic eggs.
[21] However, the Song Thrush does not demonstrate the same aggression toward the adult Cuckoo that is shown by the
Blackbird.
[22] The introduced birds in New Zealand, where the cuckoo does not occur, have, over the past 130 years, retained the ability to recognise and reject non-mimetic eggs.
[23]
Adult birds may be killed by
cats,
Little Owls and
Sparrowhawks, and eggs and nestlings are taken by
Magpies,
Jays, and, where present,
Grey Squirrels.
[24][25][26] As with other passerine birds, parasites are common, and include endoparasites, such as the
nematode Splendidofilaria (Avifilaria) maviswhose specific name
mavis derives from this thrush.
[27] A Russian study of blood parasites showed that all the Fieldfares, Redwings and Song Thrushes sampled carried haematozoans, particularly
Haemoproteus and
Trypanosoma.
[28] Ixodes ticks are also common, and can carry pathogens, including tick-borne
encephalitis in forested areas of central and eastern Europe and Russia,
[29] and, more widely,
Borrelia bacteria.
[30] Some species of
Borrelia cause
Lyme disease, and ground-feeding birds like the Song Thrush may act as a reservoir for the disease.
[31]
[edit]Feeding
The Song Thrush is
omnivorous, eating a wide range of
invertebrates, especially
earthworms and
snails, as well as soft fruit and
berries. Like its relative, the Blackbird, the Song Thrush finds animal prey by sight, has a run-and-stop hunting technique on open ground, and will rummage through leaf-litter seeking potential food items.
[9]
Snails are especially important when drought or hard weather makes it difficult to find other food. The thrush often uses a favourite stone as an "anvil" on which to smash the snail before extracting the soft body and invariably wiping it on the ground before consumption.
[20] Young birds initially flick objects and attempt to play with them until they learn to use anvils as tools to smash snails.
[32] The nestlings are mainly fed on animal food such as worms,
slugs, snails and
insect larvae.
[9]
The
Grove Snail (
Cepaea nemoralis) is regularly eaten by the Song Thrush, and its
polymorphic shell patterns have been suggested as evolutionary responses to reduce predation;
[33] however, Song Thrushes may not be the only selective force involved.
[34]
The Song Thrush has an extensive range, estimated at 10 million square kilometres (3.8 million square miles), and a large population, with an estimated 40 to 71 million individuals in Europe alone.
[1]
In the western
Palaearctic, there is evidence of population decline, but at a level below the threshold required for global conservation concern (i.e., a reduction in numbers of more than 30% in ten years or three generations) and the
IUCN Red List categorises this species as of "
Least Concern".
[1] In Great Britain and the Netherlands, there has been a more than 50% decline in population and the Song Thrush is included in
regional Red Lists.
[20][35]The decreases are greatest in farmlands (73% since the mid 1970s) and believed to be due to changes in agricultural practices in recent decades.
[5]The precise reasons for the decline are not known but may be related to the loss of hedgerows, a move to sowing crops in autumn rather than spring, and possibly the increased use of pesticides. These changes may have reduced the availability of food and of nest sites.
[36] In gardens, the use of poison bait to control slugs and snails may pose a threat
[26] and in urban areas, some thrushes are
killed while using the hard surface of roads to smash snails.
[37]
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