The
common blackbird (
Turdus merula) is a
species of
true thrush. It is also called
Eurasian blackbird (especially in North America, to distinguish it from the unrelated
New World blackbirds),
[2] or simply
blackbird where this does not lead to confusion with a
similar-looking local species. It breeds in Europe, Asia, and North Africa, and has been
introduced to Canada, United States, Mexico,
Peru,
Brazil,
Argentina,
Uruguay, the
Falkland Islands,
Chile, South Africa, Australia and New Zealand.
[3] It has a number of
subspecies across its large range; a few of the Asian subspecies are sometimes considered to be full species. Depending on
latitude, the common blackbird may be
resident, partially
migratory, or fully migratory.
The male of the
nominate subspecies, which is found throughout most of Europe, is all black except for a yellow eye-ring and
bill and has a rich, melodious
song; the adult female and juvenile have mainly dark brown
plumage. This species breeds in woods and gardens, building a neat, mud-lined, cup-shaped nest. It is
omnivorous, eating a wide range of
insects,
earthworms,
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 stay in their
territory throughout the year where the climate is sufficiently
temperate.
This common and conspicuous species has given rise to a number of
literary and cultural references, frequently related to its song.
Taxonomy and systematics
The common blackbird was described by
Linnaeus in the
10th edition of his Systema Naturae in 1758 as
Turdus merula (characterised as
T. ater, rostro palpebrisque fulvis).
[4] The binomial name derives from two
Latin words,
turdus, "thrush", and
merula, "blackbird", the latter giving rise to its French name,
merle,
[5] and its
Scots name,
merl.
[6] About 65 species of medium to large thrushes are in the genus
Turdus,
characterised by rounded heads, longish, pointed wings, and usually
melodious songs. The common blackbird seems to be closest in
evolutionary terms to the
island thrush (
T. poliocephalus) of Southeast Asia and islands in the southwest Pacific, which probably diverged from
T. merula stock fairly recently.
[7]
It may not immediately be clear why the name "blackbird", first
recorded in 1486, was applied to this species, but not to one of the
various other common black English 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". At that time,
the blackbird was therefore the only widespread and conspicuous "black
bird" in the British Isles.
[8] Until about the 17th century, another name for the species was
ouzel,
ousel or
wosel (from
Old English osle, cf. German
Amsel). 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 ouzel usage survived later in poetry, and still occurs as the
name of the closely related
ring ouzel (
Turdus torquatus), and in water ouzel, an alternative name for the unrelated but superficially similar
white-throated dipper (
Cinclus cinclus).
[9]
Juvenile T. m. merula in England
A
leucistic adult male in England with much white in the plumage
Two related Asian
Turdus thrushes, the
white-collared blackbird (
T. albocinctus) and the
grey-winged blackbird (
T. boulboul), are also named blackbirds,
[7] and the
Somali thrush (
T. (olivaceus) ludoviciae) is alternatively known as the Somali blackbird.
[10]
The
icterid
family of the New World is sometimes called the blackbird family
because of some species' superficial resemblance to the common blackbird
and other Old World thrushes, but they are not evolutionarily close,
being related to the
New World warblers and
tanagers.
[11] The term is often limited to smaller species with mostly or entirely black plumage, at least in the breeding male, notably the
cowbirds,
[12] the
grackles,
[13] and for around 20 species with "blackbird" in the name, such as the
red-winged blackbird and the
melodious blackbird.
[11]
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).
[7]
Near adult of nominate subspecies still showing some brown in the wings
Female of subspecies merula
- T. m. merula, the nominate subspecies, breeds commonly throughout much of Europe from Iceland, the Faroes 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.[7]
- T. m. azorensis is a small race which breeds in the Azores. The male is darker and glossier than merula.[14]
- T. m. cabrerae, named for Ángel Cabrera, Spanish zoologist, resembles azorensis and breeds in Madeira and the western Canary Islands.[14]
- T. m. mauretanicus, another small dark species with a glossy black male plumage, breeds in central and northern Morocco, coastal Algeria and northern Tunisia.[14]
First-summer male, probably subspecies aterrimus
- 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.[14]
- 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.[7]
- 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.[7] This is a large subspecies, with a sooty-black male and a blackish-brown female.[15]
The Asian subspecies, the relatively large
intermedius also differs in structure and voice, and may represent a distinct species.
[15] Alternatively, it has been suggested that they should be considered subspecies of
T. maximus,
[7] but they differ in structure, voice and the appearance of the eye-ring.
[15][16]
Similar species
In Europe, the common blackbird can be confused with the paler-winged first-winter
ring ouzel (
Turdus torquatus) or the superficially similar
European starling (
Sturnus vulgaris).
[17] A number of similar
Turdus thrushes exist far outside the range of the common blackbird, for example the South American
Chiguanco thrush (
Turdus chiguanco).
[18] The
Indian blackbird, the
Tibetan blackbird, and the
Chinese blackbird were formerly considered subspecies.
[19]
Description
The common blackbird of the
nominate subspecies
T. m. merula is 23.5 to 29 centimetres (9.25 to 11.4 in) in length, has a long tail, and weighs 80–125 grams (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.
[17]
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 of brown, with darker birds presumably males.
[17]
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.
[7]
Distribution and habitat
The common blackbird breeds in temperate Eurasia, North Africa, the
Canary Islands, and South Asia. It has been introduced to Australia and New Zealand.
[7] 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.
[7] 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.
[20]
Common over most of its range in woodland, the common blackbird has 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.
[21] They are often replaced by the related
ring ouzel in areas of higher altitude.
[22]
The common blackbird occurs up to 1000 metres (3300 ft) in Europe,
2300 metres (7590 ft) in North Africa, and at 900–1820 metres
(3000–6000 ft) in peninsular India and Sri Lanka, but the large
Himalayan subspecies range much higher, with
T. m. maximus breeding at 3200–4800 metres (10560–16000 ft) and remaining above 2100 metres (6930 ft) even in winter.
[7]
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.
[23] However, a 1994 record from
Bonavista, Newfoundland, has been accepted as a genuine wild bird,
[7] and the species is therefore on the
North American list.
[24]
Behaviour and ecology
Two chicks in their first hours as another egg begins to hatch
The male common 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.
[21]
The
bill's
appearance is important in the interactions of the common 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.
[25]
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.
[14]
Breeding
The male common 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.
[21] This species is monogamous, and the established pair will usually stay together as long as they both survive.
[14] Pair separation rates of up to 20% have been noted following poor breeding.
[26] Although the species is socially monogamous, there have been studies showing as much as 17% extra-pair paternity.
[27]
Nominate
T. merula may commence breeding in March, but eastern
and Indian races are a month or more later, and the introduced New
Zealand birds start nesting in August.
[7][22] The breeding 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.
[28] Sometimes the birds will nest in sheds or outbuildings where a ledge or cavity is used. The cup-shaped
nest
is made with grasses, leaves and other vegetation, bound together with
mud. It is built by the female alone. She lays three to five (usually
four) bluish-green
eggs marked with reddish-brown blotches,
[21] heaviest at the larger end;
[22] the eggs of nominate
T. merula are 2.9×2.1 centimetres (1.14×0.93 in) in size and weigh 7.2 grammes (0.25 oz), of which 6% is shell.
[29] Eggs of birds of the southern Indian races are paler than those from the northern subcontinent and Europe.
[7] 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.
[14] The nest is often ill-concealed compared with those of other species, and many breeding attempts fail due to predation.
[30]
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.
[21]
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
common blackbird's range.
[7]
A common blackbird has an average
life expectancy of 2.4 years,
[31] and, based on data from
bird ringing, the oldest recorded age is 21 years and 10 months.
[32]
Songs and calls
The first-year male common 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.
[21]
During winter, blackbirds can be heard quietly singing to themselves,
so much so that September and October are the only months which the song
cannot be heard.
[33] 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.
[34]
At least two subspecies,
T. m. merula and
T. m. nigropileus, will mimic other species of birds, cats, humans or alarms, but this is usually quiet and hard to detect.
Feeding
Adult male feeding on berries in
Lausanne, Switzerland
The common 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
amphibians and
lizards are occasionally hunted. This species will also perch in bushes to take berries and collect
caterpillars and other active insects.
[21]
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.
Natural threats
A male attempting to distract a male
kestrel close to its nest
Near human habitation the main predator of the common blackbird is
the domestic cat, with newly fledged young especially vulnerable.
Foxes and predatory birds, such as the
sparrowhawk and other
accipiters, also take this species when the opportunity arises.
[35][36]
However, there is little direct evidence to show that either predation
of the adult blackbirds or loss of the eggs and chicks to
corvids, such as the
European magpie or
Eurasian jay, have an impact on population numbers.
[28]
This species is occasionally a host of
parasitic cuckoos, such as the
common cuckoo (
Cuculus canorus), but this is minimal because the common blackbird recognizes the adult of the parasitic species and its
non-mimetic eggs.
[37] In the UK, only three nests of 59,770 examined (0.005%) contained cuckoo eggs.
[38] 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.
[39]
As with other passerine birds, parasites are common. 88% of common blackbirds were found to have
intestinal parasites, most frequently
Isospora and
Capillaria species.
[40] and more than 80% had haematozoan parasites (
Leucocytozoon,
Plasmodium,
Haemoproteus and
Trypanosoma species).
[41]
Common blackbirds spend much of their time looking for food on the
ground where they can become infested with ticks, which are external
parasites that most commonly attach to the head of a blackbird.
[42] In France, 74% of rural blackbirds were found to be infested with
Ixodes ticks, whereas, only 2% of blackbirds living in urban habitats were infested.
[42]
This is partly because it is more difficult for ticks to find another
host on lawns and gardens in urban areas than in uncultivated rural
areas, and partly because ticks are likely to be commoner in rural
areas, where a variety of tick hosts, such as foxes, deer and boar, are
more numerous.
[42] Although ixodid ticks can transmit
pathogenic viruses and bacteria, and are known to transmit
Borrelia bacteria to birds,
[43] there is no evidence that this affects the fitness of blackbirds except when they are exhausted and run down after migration.
[42]
The common blackbird is one of a number of species which has
unihemispheric slow-wave sleep. One hemisphere of the brain is effectively asleep, while a low-voltage
EEG,
characteristic of wakefulness, is present in the other. The benefit of
this is that the bird can rest in areas of high predation or during long
migratory flights, but still retain a degree of alertness.
[44]
Status and conservation
The common 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.
[1] In the western
Palaearctic, populations are generally stable or increasing,
[14]
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.
[35]
The common blackbird was introduced to Australia by a bird dealer visiting
Melbourne in early 1857,
[45] and its range has expanded from its initial foothold in Melbourne and
Adelaide to include all of south-eastern Australia, including
Tasmania and the
Bass Strait islands.
[46]
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.
[45] It is thought to spread weeds, such as
blackberry, and may compete with native birds for food and nesting sites.
[45][47]
The introduced common blackbird is, together with the native
silvereye (
Zosterops lateralis), the most widely distributed avian seed disperser in New Zealand. Introduced there along with the
song thrush (
Turdus philomelos)
in 1862, it has spread throughout the country up to an elevation of
1,500 metres (4,921 ft), as well as outlying islands such as the
Campbell and
Kermadecs.
[48]
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.
[49]
In culture
The common blackbird was seen as a sacred though destructive bird in
Classical Greek folklore, and was said to die if it consumed
pomegranate.
[50]
Like many other small birds, it has in the past been trapped in rural
areas at its night roosts as an easily available addition to the diet,
[51]
and 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:
[51]
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?[52]
The common blackbird's melodious, distinctive song is mentioned in the poem
Adlestrop 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.[53]
In the English
Christmas carol The Twelve Days of Christmas,
the line commonly sung today as "four calling birds" is believed to
have originally been written in the 18th century as "four colly birds",
an
archaism meaning "black as coal" that was a popular English nickname for the common blackbird.
[54]
The common blackbird, unlike many black creatures, is not normally seen as a symbol of bad luck,
[51] but
R. S. Thomas wrote that there is "a suggestion of dark Places about it",
[55] and it symbolised resignation in the 17th century
tragic play
The Duchess of Malfi;
[56] an alternate connotation is vigilance, the bird's clear cry warning of danger.
[56]
The common blackbird is the
national bird of Sweden,
[57] which has a breeding population of 1–2 million pairs,
[14] and was featured on a 30
öre Christmas postage stamp in 1970;
[58]
it has also featured on a number of other stamps issued by European and
Asian countries, including a 1966 4d British stamp and an 1998 Irish
30p stamp.
[59] This bird—arguably—also gives rise to the Serbian name for Kosovo, which is the possessive adjectival form of Serbian
kos ("blackbird") as in
Kosovo Polje ("Blackbird Field").
