Blackbirds

The Blackbird, Common Blackbird or Eurasian Blackbird (Turdus merula) is a thrush which breeds in Europe, Asia, and North Africa, and has been introduced elsewhere. It has a number of subspecies across its large range, but the Asian subspecies are sometimes considered to be several separate species. Depending on latitude, the Blackbird may be resident, partially migratory or fully migratory.

In the nominate subspecies, which is found throughout most of Europe, the male is all black except for a yellow eye-ring and bill, while the adult female and juvenile are mainly brown. This is a noisy species with a range of vocalisations which breeds in woods and gardens, building a neat, mud-lined, cup-shaped nest. It is omnivorous, eating a wide range of insects, earthworms, seeds, berries and fruits.

Both sexes are territorial on the breeding grounds, with distinctive threat displays, but are more gregarious during migration and in wintering areas. Pairs will stay in their territory throughout the year where the climate is sufficiently temperate. This common species has given rise to a number of literary and cultural references, frequently related to its melodious song.

Description
The Blackbird of the nominate subspecies T. m. merula is 23.5 to 29 centimetres (9.25 to 11.4 in) in length, with a long tail, and weighs 80-125 grammes (2.8 to 4.4 oz). The adult male has glossy black plumage, blackish-brown legs, a yellow eye-ring and an orange-yellow bill. The bill darkens somewhat in winter.

The adult female is sooty-brown with a dull yellowish-brownish bill, a brownish-white throat and some weak mottling on the breast. The juvenile is similar to the female, but has pale spots on the upperparts, and the very young juvenile also has a speckled breast. Young birds vary in the shade or brown, with darker birds presumably males. The first year male resembles the adult male, but has a dark bill and weaker eye ring, and its folded wing is brown, rather than black like the body plumage.

Similar species
In Europe, the Blackbird is most likely to be confused with the paler-winged first-winter Ring Ouzel (Turdus torquatus) or the superficially similar European Starling (Sturnus vulgaris). The Sri Lankan subspecies, T. m. kinsii, resembles the Sri Lanka Whistling-thrush (Myophonus blighi), and the out-of-range Tickell's Thrush (Turdus unicolor). However, the former species always has blue in the plumage, and the latter has a pale belly. A number of similar Turdus thrushes exist far outside the range of the Blackbird, for example the South American Chiguanco Thrush (Turdus chiguanco).

Distribution and habitat
The Blackbird breeds in temperate Eurasia, North Africa, the Canary Islands and southern Asia. It has been introduced to Australia and New Zealand. Populations are sedentary in the south and west of the range, although northern birds migrate south as far as northern Africa and tropical Asia in winter. Urban males are more likely to overwinter in cooler climes than rural males, an adaptation made feasible by the warmer microclimate and relatively abundant food that allow the birds to establish territories and start reproducing earlier in the year.

The Blackbird is common over most of its range in woodland, with a preference for deciduous trees with dense undergrowth. However, gardens provide the best breeding habitat with up to 7.3 pairs per hectare (nearly three pairs per acre), with woodland typically holding about a tenth of that density, and open and very built-up habitats even less. They are often replaced by the related Ring Ouzel in areas of higher altitude.

This widespread species has occurred as a vagrant in many locations in Eurasia outside its normal range, but records from North America are normally considered to involve escapees, including, for example, the 1971 bird in Quebec. However, a 1994 record from Bonavista, Newfoundland has been accepted as a genuine wild bird, and the species is therefore on the North American list.

Status
The Blackbird has an extensive range, estimated at 10 million square kilometres (3.8 million square miles), and a large population, including an estimated 79 to 160 million individuals in Europe alone. The species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e., declining more than 30% in ten years or three generations), and is therefore evaluated as Least Concern. In the western Palaearctic, populations are generally stable or increasing, but there have been local declines, especially on farmland, which may be due to agricultural policies that encouraged farmers to remove hedgerows (which provide nesting places), and to drain damp grassland and increase the use of pesticides, both of which could have reduced the availability of invertebrate food.

The Blackbird was introduced to Australia at Melbourne in the 1850s, but has expanded from its initial foothold in Melbourne and Adelaide to occur throughout south-eastern Australia, including Tasmania and the Bass Strait islands. The introduced population in Australia is considered a pest because it damages a variety of soft fruits in orchards, parks and gardens including berries, cherries, stone fruit and grapes. It is thought to spread weeds, such as blackberry, and may compete with native birds for food and nesting sites.

The introduced Blackbird is, together with the native Silvereye (Zosterops lateralis), the most widely distributed avian seed disperser in New Zealand. It eats a wide range of native and exotic fruit, and makes a major contribution to the development of communities of naturalised woody weeds. These communities provide fruit more suited to non-endemic native birds and naturalised birds, than to endemic birds.

Taxonomy
The Blackbird was described by Linnaeus in his Systema Naturae in 1758 under the genus Turdus. The binomial name derives from two Latin words, Turdus, "thrush", and merula, "blackbird", the latter giving rise to the French name for this species, merle.

It is not immediately clear in modern English why "Blackbird", first recorded in 1486, was applied to this species, but not to one or other common black European birds, such as the Carrion Crow, Raven, Rook or Jackdaw. However, in Old English, and in modern English up to about the 18th Century, "bird" was used only for smaller or young birds, and larger ones, such as crows were called "fowl". The Blackbird was therefore the only widespread and conspicuous "black bird" in the British Isles.

Until about the 17th century, another usual name for the species was ouzel, ousel or wosel (from Old English osle). Another variant occurs in Act 3 of Shakespeare's A Midsummer Night's Dream, where Bottom refers to The Woosell cocke, so blacke of hew, With Orenge-tawny bill. The ousel usage survived later in poetry, and still occurs as the name of the closely related Ring Ouzel, and in Water Ouzel, an alternative name for the unrelated but superficially similar White-throated Dipper (Cinclus cinclus).

Two related Asian Turdus thrushes, the White-collared Blackbird and the Grey-winged Blackbird are also named as blackbirds, and the Somali Thrush is alternatively known as the Somali Blackbird.

Around 20 species of the New World icterid family are named as blackbirds because of their superficial resemblance to the Old World thrushes, but they are not closely related, being nearer to the New World warblers and tanagers in evolutionary terms. They include the Red-winged Blackbird (Agelaius phoeniceus), Red-breasted Blackbird (Sturnella militaris), Yellow-headed Blackbird (Xanthocephalus xanthocephalus) and the Melodious Blackbird (Dives dives).

Subspecies
As would be expected for a widespread passerine bird species, several geographical subspecies are recognised. The treatment of subspecies in this article follows Clement et al (2000).
 * T. m. merula, the nominate subspecies, breeds commonly throughout much of Europe from Iceland, the Faeroes and the British Isles east to the Ural Mountains and north to about 70 N, where it is fairly scarce. A small population breeds in the Nile valley. Birds from the north of the range winter throughout Europe and around the Mediterranean including Cyprus and North Africa. The introduced birds in Australia and New Zealand are of the nominate race.
 * T. m. azorensis is a small race which breeds in the Azores. The male is darker and glossier than merula.
 * T. m. cabrerae, named for Ángel Cabrera, Spanish zoologist, resembles azorensis and breeds in Madeira and the western Canary Islands.
 * T. m. mauretanicus, another small dark species with a glossy black male plumage, breeds in central and northern Morocco, coastal Algeria and northern Tunisia.
 * T m. aterrimus breeds in Hungary, south and east to southern Greece, Crete northern Turkey and northern Iran. It winters in southern Turkey, northern Egypt, Iraq and southern Iran. It is smaller than merula with a duller male and paler female plumage.
 * T. m. syriacus breeds on the Mediterranean coast of southern Turkey south to Jordan, Israel and the northern Sinai. It is mostly resident, but part of the population moves south west or west to winter in the Jordan Valley  and in the Nile Delta of northern Egypt south to about Cairo. Both sexes of this subspecies are darker and greyer than the equivalent merula plumages.
 * T. m. intermedius is an Asiatic race breeding from Central Russia to Tajikistan, western and north east Afghanistan, and eastern China. Many birds are resident but some are altitudinal migrants and occur in southern Afghanistan and southern Iraq in winter. This is a large subspecies, with a sooty-black male and a blackish-brown female. [[Image:Eurasian blackbird maximus cropped.jpg|thumb|Female subspecies maximus, at 3,400 m (11000 ft) in [[Himachal Pradesh]]]]
 * T. m. maximus is a large montane subspecies found from eastern Afghanistan east through the Himalayas between 3200 and 4800 metres (10,560-16,000 ft) to Sikkim, Assam, southern Tibet and western Szechwan, China. It is an altitudinal migrant, and in winter occurs down to 2100 metres (6930 ft) in south east Tibet, but not below 3000 metres (9900 ft) further west. The male is black and the female very dark brown. It is the only subspecies without a yellow or orange eye-ring.
 * T. m. mandarinus breeds throughout much of south, central and east China . It is a partial migrant to Hong Kong and south to Laos and Vietnam. The male is sooty black, and the female is similar but browner, and paler on the underparts. It is a large subspecies.
 * T. m. sowerbyi, named for James Sowerby, British naturalist and illustrator, breeds from east Szechwan to Guizhou. It is partially migratory, with some individuals spending the winter in south China and north Indochina. It resembles mandarinus, but is smaller and darker below.
 * T. m. nigropileus is resident up to about 1820 metres (6000 ft) in the Western Ghats of western India and the northern and central parts of the Western Ghats. The male is brownish slate-grey with a dark cap, and the female is mid-brown, paler below. It is small with a relatively broad yellow eye-ring.
 * T. m. spencei, named for William Spence, British entomologist, is very similar to  nigropileus, but has a less distinct cap. It is resident in the highlands of eastern India. It is of dubious validity, and is often included in nigropileus.
 * T. m. simillimus is a common resident of the hills in Kerala and Tamil Nadu, south west India. It is darker than spencei.
 * T. m. bourdilloni, named for Thomas Fulton Bourdillon, Conservator of Forests in the then princely state of Travancore, is a common resident of the hills above 900 metres (3000 ft) in southern Kerala and Tamil Nadu. It resembles simillimus, but the male is uniform slate brown.
 * T. m. kinnisii named for Dr John Kinnis, surgeon to the forces in what was then Ceylon, breeds in the hills of Sri Lanka above 900 metres (3000 ft). The male is uniformly blue-grey, and the female is similar but browner. Size as in nigropileus, but eye-ring more reddish-orange.

The taxonomy, especially of the Asian subspecies, is complex. The subspecies from most of the Indian subcontinent, simillimus, nigropileus, bourdiloni, spencei, and kinnissi, are small, only 19-20 centimetres (7.5-8 in) long, and have broad eye-rings. They also differ in proportions, wing formula, egg colour and voice from the other subspecies of the Blackbird. They are therefore sometimes considered a separate species, the Indian Blackbird (T. simillimus). The Himalayan subspecies maximus is strikingly different from the simillimus group, being relatively large at 23-28 centimetres (9-11 in) length. It differs from all other subspecies of the Blackbird by its complete lack of eye-ring and reduced song. It is therefore sometimes considered a separate monotypic species, the Tibetan Blackbird (T. maximus). The remaining Asian subspecies, the relatively large intermedius and mandarinus, and the smaller sowerbyi, also differ in structure and voice, and may represent a third species, the Chinese Blackbird (T. mandarinus). Alternatively, it has been suggested that they should be considered subspecies of T. maximus, but they differ in structure, voice and the appearance of the eye-ring.

Behaviour
The male Blackbird defends its breeding territory, chasing away other males or utilising a "bow and run" threat display. This consists of a short run, the head first being raised and then bowed with the tail dipped simultaneously. If a fight between male Blackbirds does occur it is usually short and the intruder is soon chased away. The female Blackbird is also aggressive in the spring when it competes with other females for a good nesting territory, and although fights are less frequent, they tend to be more violent.

The bill’s appearance is important in the interactions of the Blackbird. The territory-holding male responds more aggressively towards models with orange bills than to those with yellow bills, and reacts least to the brown bill colour typical of the first-year male. The female is, however, relatively indifferent to bill colour, but responds instead to shinier bills.

As long as winter food is available, both the male and female will remain in the territory throughout the year, although occupying different areas. Migrants are more gregarious, travelling in small flocks and feeding in loose groups in the wintering grounds. The flight of migrating birds comprises bursts of rapid wing beats interspersed with level or diving movement, and differs from both the normal fast agile flight of this species and the more dipping action of larger thrushes.

Breeding
The male Blackbird attracts the female with a courtship display which consists of oblique runs combined with head-bowing movements, an open beak, and a "strangled" low song. The female remains motionless until she raises her head and tail to permit copulation. This species is monogamous, and the established pair will stay together as long as they both survive.

The pair prospect for a suitable nest site in a creeper or bush, favouring evergreen or thorny species such as ivy, holly, hawthorn, honeysuckle or pyracantha, and the female builds a neat cup-shaped nest from grasses and similar vegetation, which she then lines with mud or muddy leaves. Breeding may commence in March in the British Isles. She lays three to five (usually four) bluish-green eggs marked with reddish-brown blotches. Spotting may be heavier at the larger end. The eggs of birds of the southern Indian races are paler than those from the northern subcontinent and Europe. The eggs (nominate merula) are 2.9 x 2.1 centimetres (1.14 x 0.93 in) in size and weigh 7.2 grammes (0.25 oz), of which 6% is shell. The female incubates for 12-14 days before the altricial chicks are hatched naked and blind. Fledging takes another 10-19 (average 13.6) days, with both parents feeding the young and removing faecal sacs.

The young are fed by the parents for up to three weeks after leaving the nest, and will follow the adults begging for food. If the female starts another nest, the male alone will feed the fledged young. Second broods are common, with the female reusing the same nest if the brood was successful, and three broods may be raised in the south of the Blackbird's range.

Montane subspecies, such as maximus have a shorter breeding season, smaller clutches (2–4 eggs, averaging 2.86), but larger eggs than merula. They produce just one brood per year, and have a slightly shorter incubation period of 12–13 days, but a longer nestling period (16–18 days).

A Blackbird has an average life expectancy of 2.4 years, and, based on data from bird ringing, the oldest recorded age is 21 years and 10 months.

Songs and calls
The first-year male Blackbird of the nominate race may start singing as early as late January in fine weather in order to establish a territory, followed in late March by the adult male. The male's song is a varied and melodious low-pitched fluted warble, given from trees, rooftops or other elevated perches mainly in the period from March to June, sometimes into the beginning of July. It has a number of other calls, including an aggressive seee, a pook-pook-pook alarm for terrestrial predators like cats, and various chink and chook, chook vocalisations. The territorial male invariably gives chink-chink calls in the evening in an (usually unsuccessful) attempt to deter other Blackbirds from roosting in its territory overnight. Like other passerine birds, it has a thin high seee alarm call for threats from birds of prey since the sound is rapidly attenuated in vegetation, making the source difficult to locate.

At least two subspecies, nominate merula and nigropileus of India, will mimic birds, cats, humans or alarms, but this is usually quiet and hard to detect. The large mountain races, especially maximus, have comparatively poor songs, with a limited repertoire compared with the western, peninsular Indian and Sri Lankan taxa.

Feeding
The Blackbird is omnivorous, eating a wide range of insects, earthworms, seeds and berries. It feeds mainly on the ground, running and hopping with a start-stop-start progress. It pulls earthworms from the soil, usually finding them by sight, but sometimes by hearing, and roots through leaf litter for other invertebrates. Small vertebrates such as frogs, tadpoles and lizards are occasionally hunted. This species will also perch in bushes to take berries and collect caterpillars and other active insects.

Animal prey predominates, and is particularly important during the breeding season, with windfall apples and berries taken more in the autumn and winter. The nature of the fruit taken depends on what is locally available, and frequently includes exotics in gardens. In northern India, banyan and mulberry fruits are frequently eaten, with Erythrina and Trema species featuring further south.

Natural threats
The main predator of the Blackbird is the domestic cat, but foxes and predatory birds like the Sparrowhawk and other accipiters also take this species when the opportunity arises. However, there is little direct evidence to show that either predation of the adults or loss of the eggs and chicks to corvids like the European Magpie or Eurasian Jay have a direct impact on population numbers.

This species is occasionally a host of parasitic cuckoos, such as the Common Cuckoo Cuculus canorus, but this is minimal because the Blackbird recognizes the adult of the parasitic species and its non-mimetic eggs. The introduced merula Blackbird in New Zealand, where the cuckoo does not occur, has, over the past 130 years, lost the ability to recognize the adult Common Cuckoo but still rejects non-mimetic eggs.

As with other passerine birds, parasites are common. 88% of blackbirds were found to have intestinal parasites, most frequently Isospora and Capillaria species. and more than 80% had haematozoan parasites. External infestation by Ixodes ticks were found to be much higher (74%) in rural habitats than in urban (2%). Given that ixodid ticks are known to transmit pathogens, including the spirochaete responsible for Lyme disease, the lower infestation rate could be a factor in the higher densities and longer survival of Blackbirds in urban areas.

In culture
The Blackbird was seen as a sacred though destructive bird at the same time in Classical Greek folklore, and was said to die if it consumed pomegranate. Later, in medieval times, the  conceit of placing live birds under a pie crust just before serving may have been the origin of the familiar nursery rhyme: Sing a song of sixpence, A pocket full of rye; Four and twenty blackbirds baked in a pie! When the pie was opened the birds began to sing, Oh wasn't that a dainty dish to set before the king? Like many other small birds, blackbirds have in the past been trapped in rural areas at their night roosts as an easily available addition to the diet.

The Blackbird lives in close association with humans, and its melodious, distinctive song is the theme of the poem Adelstrop by Edward Thomas; And for that minute a blackbird sang Close by, and round him, mistier, Farther and farther, all the birds Of Oxfordshire and Gloucestershire. The Blackbird’s song is also recalled in the Beatles track Blackbird: Blackbird singing in the dead of night, Take these broken wings and learn to fly All your life, You were only waiting for this moment to arise.

The Blackbird, unlike many black creatures, is not normally seen as a symbol of bad luck, but R. S. Thomas wrote that there is "a suggestion of dark Places about it".

The Blackbird is the national bird of Sweden, which has a breeding population of 1-2 million pairs, and was featured on a 30 öre Christmas postage stamp in 1970.