Common blackbird

Name and taxonomy

Carl Linnaeus described the species in 1758 as Turdus merula. Both words are Latin, and they mean thrush and blackbird. The second word gives the French merle and the Scots merl. The English name blackbird was first written down in 1486. North Americans say Eurasian blackbird, to keep it apart from their own unrelated blackbirds.

The name seems odd, because crows and rooks are black too. In older English, the word bird meant only a small bird, and a crow counted as a fowl. This was therefore the only common black bird in Britain by that rule. An older name for the species was the ouzel, from Old English osle. Shakespeare used it in A Midsummer Night's Dream, and the ring ouzel still carries it.

Evolution and relatives

The genus Turdus holds about 65 thrushes with round heads, pointed wings and good voices. The song thrush and the mistle thrush split off early from the Eurasian line. This bird came by a different route, through ancestors that reached the Canary Islands from Africa. Those birds then crossed into Europe. The island thrush of Southeast Asia and the Pacific is a close and fairly recent relative.

Several Asian thrushes also carry the name blackbird. The Indian, Tibetan and Chinese blackbirds were once treated as subspecies of this one. All three are now handled as separate species. Seven or more geographic subspecies remain, and the Central Asian intermedius may be another species. The New World blackbirds are not thrushes at all, and sit near the warblers and tanagers.

Appearance

The adult male is glossy black with blackish-brown legs. His bill is orange-yellow and darkens a little in winter. A clean yellow ring circles the eye. The average weight is about 102 grams and the average length about 25 centimetres. The wingspan runs from 34 to 38 cm.

The female is sooty brown with a dull yellowish-brown bill. Her throat is brownish white and her breast carries faint mottling. A juvenile looks like the female but shows pale spots above and a speckled breast. Darker young birds are probably males. A first-year male has a dark bill, a weak eye-ring and brown folded wings.

Bill colour matters to the birds themselves. A male defending ground reacts hardest to a model with an orange bill. He reacts least to the brown bill of a first-year male. Females ignore the hue and respond to how glossy the bill is. The colour itself comes from carotenoid pigments in the food the male finds.

Habitat and range

The species breeds across temperate Eurasia, North Africa, the Canary Islands and South Asia. Birds in the south and west stay put all year. Northern birds move south to North Africa and tropical Asia for the winter. Ringing shows blackbirds crossing from southern Norway to Scotland and on to Ireland. Females in Scotland and northern England migrate more often than males do.

Deciduous woodland with thick undergrowth is the natural habitat. Gardens beat it, and hold up to 7.3 pairs per hectare. Woodland holds roughly a tenth as many, and open or heavily built ground fewer still. Parks and hedgerows hold birds as well. At higher altitude the ring ouzel replaces it.

The bird reaches 1,000 metres in Europe and 2,300 m in North Africa. Himalayan populations live far higher, from 3,200 to 4,800 m in the breeding season. Urban males are more likely than country males to stay north through the winter. Warmer streets and steady food let them hold a territory and breed earlier. Records from North America are usually escaped birds, though one Newfoundland bird of 1994 was accepted as wild.

Diet and feeding

The blackbird is an omnivore and eats insects, earthworms, seeds and berries. It works the ground, running and then hopping in short broken bursts. It pulls worms out of the soil, finding them by sight and sometimes by ear. It turns over leaf litter for beetles, snails, spiders and caterpillars. Small amphibians, lizards and even small mammals are taken now and then.

Fruit probably matters most in autumn and winter. Hawthorn, sloe, ivy, elder, bramble and dog rose all appear in the diet. The bird prefers large fruit with few seeds that pass easily through the gut. It perches in a bush to reach berries rather than taking them from the ground. Garden feeders now supply a further share of the food near houses.

Behaviour and social life

A male defends his ground by chasing rivals or by a bow and run display. He runs a short way, lifts his head, then bows it and dips the tail together. Real fights are short, and the intruder usually leaves at once. Females fight less often over nest sites, but their fights are more violent. Nests sit at least 30 metres apart, and a pair uses about 12,700 square metres.

A pair holds its territory all year where winter food lasts. The two birds then use different parts of the same ground. Migrants are far more sociable and travel in small flocks. They feed in loose groups on the wintering ground. Autumn and winter journeys cover 800 to 2,000 kilometres.

Migrating flight comes in bursts of fast beats with level or dipping glides between. That differs from the quick agile flight the bird uses at home. The blackbird can sleep with one half of the brain at a time. The other half stays awake, which allows rest in dangerous places and on long flights. Heavy human traffic pushes birds to quieter ground and cuts their feeding time.

Communication and senses

The male sings a varied, low-pitched fluted warble. He sings from trees, rooftops and other high perches, mainly from March to June. A first-year male may start as early as late January in mild weather. September and October are the only months with no song at all. In winter the birds sing quietly to themselves.

The calls appear as useful as the song. A pook-pook-pook warns of a cat or another ground hunter. A thin high seee marks a bird of prey, and vegetation muffles it so the caller is hard to locate. Chink-chink calls at dusk try to move other blackbirds out of the roost. That attempt usually fails.

The bird copies sounds it hears around it. Other birds' songs, human whistling and car alarms all turn up in its repertoire. City birds sing at a higher pitch than country birds, by about 198 hertz on average. Traffic noise appears to drive that shift. Pitch and pattern change again when a male means to fight.

Reproduction and life cycle

The male courts with slanting runs, head bows, an open beak and a low strangled song. The female stays still until she lifts her head and tail to allow mating. Pairs are socially monogamous and usually stay together for life. Separation rates of up to 20 per cent follow a bad breeding season. Studies have found as much as 17 per cent of chicks fathered outside the pair.

European birds may start nesting in March, and Asian races a month or more later. New Zealand birds nest in August, which is late winter there. The female alone builds a cup of grass, leaves and other plants bound with mud. She sites it in ivy, holly, hawthorn or another thick evergreen or thorny plant. Sheds and outbuildings serve too, wherever a ledge or cavity offers itself.

A clutch is three to five eggs, and four is the usual number. The eggs are bluish green with reddish-brown blotches, about 2.9 by 2.1 centimetres, and weigh 7.2 grams. The female incubates for 12 to 14 days, and the chicks hatch naked and blind. Both parents feed them for another 10 to 19 days until they leave the nest. Two broods are normal and three are possible in the south, and average life expectancy is 2.4 years.

Predators and threats

Near houses the domestic cat is the main predator. Newly fledged young are the most vulnerable stage. Sparrowhawks, other hawks and foxes take birds when the chance comes. Magpies, jays and the garden dormouse rob nests, which are often poorly hidden. There is little evidence that any of this reduces the overall population.

Parasites may be a heavier burden than predators. Intestinal parasites were found in 88 per cent of birds examined, and blood parasites in more than 80 per cent. In France, ticks infested 74 per cent of country blackbirds but only 2 per cent of city birds. The common cuckoo rarely succeeds here, because the blackbird knows the adult and rejects the egg. Only three of 59,770 British nests examined held a cuckoo egg.

Population and conservation

The range covers an estimated 32.4 million square kilometres. Europe alone holds 79 to 160 million birds, so the IUCN rates the species Least Concern. Numbers in the western Palearctic are stable or rising overall. Farmland populations have dropped in places, after hedgerows were removed and damp grassland drained. More pesticide has also cut the supply of insects and worms.

A newer threat is the Usutu virus, which mosquitoes carry. It was found in Italy in 1996 and has since reached Germany and the United Kingdom. The virus has cut blackbird numbers sharply in parts of Europe. Finland, Portugal and Israel all rate the species Least Concern on their own lists. iNaturalist holds 263,570 records of the bird.

Relationship with humans

Few wild birds appear to live as close to people as this one. It visits feeders in city parks and gardens across Europe. ADW records no negative economic effect of the species in its native range. Country people once trapped blackbirds at their night roosts for food. Researchers use the bird to measure how human disturbance changes feeding behaviour.

Abroad the record is different. A bird dealer released blackbirds in Melbourne in early 1857, and they spread across south-eastern Australia. Australians treat the introduced bird as a pest of berries, cherries, stone fruit and grapes. It also spreads weeds such as blackberry and competes with native birds for food and nest sites. New Zealand received the species in 1862, and it now reaches 1,500 metres and outlying islands there.

In New Zealand the blackbird is the most widespread bird that spreads seed. It shares that role with the native silvereye. It eats native and exotic fruit alike and helps woody weeds establish. Those weed thickets then feed introduced birds better than they feed endemic ones. One useful effect and one harmful effect appear to come from the same habit.

In culture and myth

In Classical Greek tradition the blackbird was sacred and destructive at once. The story held that the bird would die if it ate pomegranates. Unlike most black animals, it is not usually read as a sign of bad luck. The poet R. S. Thomas found a hint of dark places about it. In the seventeenth-century play The Duchess of Malfi it stands for resignation.

The best-known English reference is the rhyme Sing a Song of Sixpence. It was printed about 1744, and the four and twenty blackbirds replaced naughty boys about 1780. Cooks really did serve pies holding live birds, a trick recorded from 1549. Songbirds flew out of the napkins at a royal wedding in 1600, that of Marie de Medici. Iona and Peter Opie collected many readings of the rhyme, none of them supported by evidence.

The carol The Twelve Days of Christmas may once have named this bird. Four calling birds is thought to have been four colly birds, meaning black as coal. Paul McCartney recorded the Beatles song Blackbird on 11 June 1968, with a real blackbird in the background. He has said the song used the bird as a symbol for black people in the southern United States. Sweden made the blackbird its national bird and put it on a Christmas stamp in 1970.