Common starling

• 1. Introduction

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  The common starling, Sturnus vulgaris, once convinced a famous composer to buy it on the spot. Mozart heard one in a shop singing a phrase from a piece he had finished only six weeks earlier. No audience had yet heard that piece. He took the bird home and grew very attached to it. When it died three years later, he arranged an elaborate funeral.

  The singer was a glossy black bird about 20 cm long. It is native to Europe and across the Palearctic to western Mongolia. People have carried it to Australia, New Zealand, Canada, the United States, Mexico, Argentina, South Africa and Fiji. How does such a small bird pick up a tune so quickly? What lets thousands of them wheel through the sky as one shape, with no leader? And how did a bird that settlers once welcomed end up on the IUCN list of the world's 100 worst invasive species?

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• 2. Probing for a Living

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  A common starling weighs between 58 and 101 g and measures 19 to 23 cm, with a wingspan of 31 to 44 cm. Its plumage is black with a purple or green sheen. In winter it looks spangled with white, because fresh feathers grow in after the yearly moult in late summer, each tipped in white or buff. Through the breeding season those tips largely wear away, and the bird looks darker and smoother.

  The bill changes with the seasons. In winter it is brownish-black. In summer, females have lemon yellow bills with pink bases, while males have yellow bills with blue-grey bases. Young birds are grey-brown and usually resemble adults by their first winter. Their eyes give away their sex. Irises are rich brown in males and mouse-brown or grey in females. Judging the contrast between iris and pupil identifies sex correctly 97% of the time, and 98% when throat-feather length is added.

  On the ground, the starling walks or runs rather than hopping, with a waddling gait. In the air it beats triangular wings very fast and glides now and then. On migration it can fly at 60 to 80 km/h and cover up to 1,500 km.

  The skull is where the starling stands out. In this species the muscles that open the jaw are enlarged and the skull is narrow. That lets the eye swing forward to peer down the length of the bill. The bird pushes its bill into the soil and then pries it open, widening a hole to search for hidden prey. Konrad Lorenz first described this behaviour and gave it the German name zirkeln. Starlings also use it to tear holes in plastic garbage bags.

  Probing is only one of three techniques. Hawking is catching insects out of the air. Lunging is a sudden strike at a moving invertebrate on the ground. Young birds are slow to perfect probing, so their diet contains fewer insects. Adults take spiders, crane flies, beetles, wasps and ants, along with earthworms, snails, small lizards and amphibians. They also eat grain, seeds, fruit, nectar and scraps of human food.

  Starlings and their relatives do not easily digest foods very high in sucrose, though grapes and cherries are fine. Foraging flocks use roller-feeding, in which birds at the back keep flying forward to the front, where the food is best. Many starlings feed beside grazing animals, sometimes perched on their backs, picking off external parasites. One isolated population, on the Azores, has a more troubling menu: it eats the eggs of the endangered roseate tern. Culling is being introduced there before the terns return each spring.

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• 3. Voice and Mimicry

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  A male starling's song bout can run for a minute or more, and it follows a fixed order of four parts. First come pure whistles. Next is the long middle stretch, built from variable sequences that borrow snatches of other birds' songs and of natural and man-made noises. Repeated clicks follow. A final burst of high-pitched notes closes the performance.

  What the bird copies depends more on the structure and simplicity of a sound than on how often it hears it. A wild starling has been seen imitating a sound it heard only once. The best singers hold up to 35 variable song types and as many as 14 types of clicks. Older birds usually know more than younger ones.

  The repertoire has a practical payoff. Males with longer bouts and bigger repertoires attract mates earlier and raise more young. Females seem to favour complex song, perhaps as a sign of experience or long life. Males also have a syrinx, the bird's voice organ, about 35% larger than the female's. That gap is modest next to the zebra finch, where the male's syrinx is 100% larger. Some males even fly to the nest and sing from the entrance, apparently to lure a female inside.

  Starlings have eleven other described calls, including a flock call, a threat call and a snarl call. The alarm call is a harsh scream. Roosting flocks chatter loudly enough to irritate people living nearby.

  Human writers noticed the mimicry long ago. In the medieval Welsh Mabinogion, Branwen tames a starling and teaches it words. She sends it across the Irish Sea with a message to her brothers, Bran and Manawydan, who sail from Wales to Ireland to rescue her. Pliny the Elder claimed starlings could learn whole sentences in Latin and Greek. In Henry IV, Shakespeare gives Hotspur a plan for revenge: "Nay I'll have a starling shall be taught to speak nothing but Mortimer, and give it to him to keep his anger still in motion."

  It has been suggested that Mozart's A Musical Joke, catalogued as K. 522, imitates the comical, inconsequential style of starling song. People who keep starlings say the birds pick up phrases easily. The words mean nothing to the bird, so it mixes them up or uses them at odd moments. Some imitations are so good that strangers have looked in vain for the person they thought they heard.

  Lorenz, in his book King Solomon's Ring, called the starling "the poor man's dog" and "something to love." Nestlings are easy to get and, once hand-reared, easy to keep. As a laboratory bird, the starling ranks second in numbers only to the domestic pigeon.

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• 4. Murmurations

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  Over the marshlands of southwestern Jutland, in Denmark, more than a million starlings gather before sunset each spring. They stay in March until the northern Scandinavian birds leave for their breeding grounds by mid-April. Their swarming makes shifting shapes against the sky, which locals call sort sol, meaning black sun.

  In the United Kingdom, mid-winter flocks before sundown range from five to fifty thousand birds. These are commonly called murmurations. In flight, a flock forms a tight sphere that expands, contracts and changes shape, with no leader that anyone can identify. Each bird adjusts its course and speed according to its closest neighbours.

  The dense formation is thought to be a defence against peregrine falcons and Eurasian sparrowhawks. When the wings of a whole flock beat together, they make a distinctive whooshing sound that carries hundreds of metres.

  The largest gatherings happen at roosts in city centres, woodlands and reedbeds, and they can reach 1.5 million birds. Droppings there can pile up to 30 cm deep. That much waste, with its concentrated chemicals, can kill trees. In smaller amounts the same droppings work as fertiliser. Some woodland managers try to shift a roost from one part of a wood to another, collecting the soil benefit while avoiding the toxic heaps.

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• 5. Nest and Brood

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  An unpaired male starling starts the courtship by finding a cavity and building in it. He often decorates the nest with flowers and fresh green material, and the female pulls it apart once she accepts him. The quantity of greenery matters little, but herbs seem to matter. The scent of plants such as yarrow acts as an attractant to females. The male sings through much of the building, and more when a female approaches.

  The finished nest is made of straw, dry grass and twigs, lined with feathers, wool and soft leaves. Building takes four or five days. Hollow trees, buildings, stumps and nest-boxes all serve. The Shetland subspecies, S. v. zetlandicus, usually nests in cliff crevices, a site the nominate form rarely uses.

  Most broods are raised by one male and one female, though some pairs have a helper. Some males also mate with a second female while the first is still sitting. The second nest does worse than the first, and the male's success is better if he stays with one mate.

  The female lays four or five glossy, pale blue eggs, one a day, and replaces any that are lost. Blue is relatively easy to see in low light, which may explain the colour. Incubation lasts thirteen days. The female does most of it and is the only parent on the eggs at night, while the male returns to the communal roost. A pair can raise up to three broods a year, though two is typical, and only one north of 48 degrees north.

  The chicks hatch blind and naked. They grow down within seven days and can see by day nine. For about six days the adults carry away their droppings. After that the chicks can regulate their own temperature, and the adults largely stop. They stay in the nest for three weeks, and parents keep feeding them for another one or two weeks outside it. The yard is crowded with cheats. Unpaired females, called floaters, sometimes lay eggs in other pairs' nests. Fledglings have even been reported invading nests and evicting a new brood.

  The odds are hard. Between 48% and 79% of nests fledge young, but only 20% of nestlings live to breeding age. Adult survival is closer to 60%. The average life span is about two to three years, and the record is 22 years and 11 months.

  That low survival of young birds lies behind a steep fall in northern Europe. Numbers in the United Kingdom dropped by more than 80% between 1966 and 2004. Sweden, Finland, Karelia in northern Russia and the Baltic States have seen major declines since 1980. Several countries now red-list the bird after falls of more than 50%. Intensive farming has shrunk the pasture and meadow, and with it the grassland invertebrates that nestlings need to thrive. Even so, the world population was estimated at 310 million in 2004, so the IUCN rates the species as of least concern.

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• 6. Hunters and Hosts

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  Northern goshawks, Eurasian sparrowhawks and peregrine falcons hunt adult starlings, along with Eurasian hobbies and common kestrels. Slower raptors such as red and black kites and the common buzzard tend to take fledglings and juveniles. A starling flock usually answers by taking off, and few birds of prey match its agility in the air. At night, roosting groups face owls, from the little owl to the Eurasian eagle-owl.

  In North America, more than twenty species of hawk, owl and falcon occasionally take starlings. The most regular killers of adults are probably urban peregrines and merlins. Common mynas sometimes evict starlings from nests, and the lesser honeyguide uses the starling as a host for its eggs. Yet starlings are more often the aggressors, especially against other starlings and woodpeckers. Climbing mammals such as raccoons, squirrels and small mustelids raid their nests, and a careless bird can be caught by a cat.

  Parasites are everywhere. A survey of three hundred starlings from six US states found that every bird carried at least one kind. External fleas, mites or ticks were on 99% of them, and 95% held internal parasites, mostly worms. One bird with a deformed bill was heavily infested with lice, probably because it could not preen them away.

  The hen flea is the commonest flea in starling nests. The hen mite lives there too, and a predatory mite, Androlaelaps casalis, feeds on it. That natural pest control may explain why starlings are willing to reuse old nests. A fly called Carnus hemapterus snaps off host feathers and lives on the fats released by growing plumage. A brilliant scarlet nematode, Syngamus trachea, travels from the lungs to the windpipe and can suffocate its host. In Britain, only the rook is as heavily infested as the starling.

  Starlings can also catch avian tuberculosis, avian malaria and retrovirus-induced lymphomas. Captive birds often store too much iron in the liver. Keepers have found a simple remedy, which is adding black tea leaves to the food.

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• 7. Carried Abroad

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  Within Europe, the starling was already on the move in the 19th century. Around 1830 it spread into Ireland and parts of Scotland where it had been absent. It has bred in northern Sweden since 1850 and in Iceland since 1935. It began breeding in Iberia in 1960. There it meets the spotless starling, a close relative that has pushed north since the 1950s. Both species advance at about 4.7 km a year, and competition where they overlap has slowed them further.

  The far longer journeys were deliberate. In New Zealand in 1862, the Nelson Acclimatisation Society brought starlings from Europe, along with house sparrows. Settlers had cleared the bush, and their new crops were swarming with caterpillars and other insects. The birds spread across the country, from the Kermadec Islands in the north to Macquarie Island in the far south.

  In Australia, starlings reached Melbourne in 1857 and Sydney two decades later. Settlers hoped they would eat crop pests and pollinate flax. Farms received nest-boxes for the new arrivals, and acclimatisation committees helped establish populations in the southeast by the 1880s. By the 1920s the birds were widespread across Victoria, Queensland and New South Wales, and were already seen as pests.

  Western Australia is the exception. Starlings were first seen in Albany in 1917. The state had banned imports in 1895, and the wide, dry Nullarbor Plain helps as a barrier. Control measures there have killed 55,000 birds over three decades. New flocks arriving from the east are shot, and less cautious juveniles are trapped. By 2009 only 300 birds remained, and the state committed a further A$400,000 to the eradication programme.

  In North America, about 60 starlings were released into New York's Central Park in 1890 by Eugene Schieffelin, president of the American Acclimatization Society. Around the same time, the Portland Song Bird Club released 35 pairs in Portland, Oregon. A popular story says Schieffelin wanted to bring every bird named in Shakespeare to America. That claim has been traced to a 1948 essay by the naturalist Edwin Way Teale, whose notes suggest he was only speculating. The population there is now estimated at 150 million, from southern Canada and Alaska to Central America.

  Other introductions followed the same logic. Cecil Rhodes introduced the starling to South Africa in 1897. In 1901, the people of Saint Kitts petitioned the Colonial Secretary for a "government grant of starlings to exterminate" a grasshopper outbreak. Jamaica received birds in 1903. In Fiji, starlings appear to have arrived on their own in 1925.

  The story is still being written in South America. Five birds shipped from England landed near Lago de Maracaibo in Venezuela in November 1949 and then vanished. In 1987, a small population was seen nesting in gardens in Buenos Aires. Despite early eradication attempts, the Argentine birds have since spread at an average of 7.5 km a year, staying within 30 km of the Atlantic coast.

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• 8. Pest and Ally

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  In the former Soviet Union, about 25 million nest boxes were put up for starlings. The reason was their appetite for pests such as wireworms. In New Zealand the birds proved effective against the grass grub, and even the US Department of Agriculture acknowledges that they eat vast numbers of insects.

  The costs are heavy. In the United States, agricultural damage by starlings is estimated at about US$800 million a year. Together with the house sparrow, they are blamed for roughly US$1 billion in crop damage annually. Flocks strip grapes, olives, cherries, peaches and tomatoes, and pull up newly sown grain. In 1968, bird damage to grapes cost up to $4.4 million, nearly 17% of the crop. At feed troughs they eat the high-protein supplements added to cattle rations, and in 1968 that cost $84 per 1,000 starlings. In eastern Australia, they are thought to have spread bridal creeper, blackberry and boneseed through their droppings.

  Where no other starlings live, the newcomer takes over nest holes. In North America it can affect chickadees, nuthatches, woodpeckers and purple martins. In Australia it competes with crimson and eastern rosellas. A starling will seize a tree hollow and stuff it with bedding, far more than native parrots use.

  On 1960 in Boston, Eastern Air Lines Flight 375 flew into a flock. The turboprop airliner plunged into the sea at Winthrop Harbor, and 62 people died. Between 1990 and 2001, starlings and New World blackbirds caused 852 reported aircraft incidents, 39 of them with major damage totalling $1,607,317. Droppings can also carry the fungus behind histoplasmosis. A Nebraska manufacturing facility lost 10,000 pigs to an outbreak, valued at $1 million in 2014.

  Laws vary widely. Spain hunts starlings commercially, with a closed season. France classes them as a pest, with a season covering most of the year. In Great Britain the Wildlife and Countryside Act 1981 makes it illegal to intentionally kill, injure or take one. Because starlings migrate, birds culled in one place may have come from far away, so control often achieves little in Europe.

  In 1949, so many starlings landed on the hands of Big Ben in London that the clock stopped. Netting, repellent chemicals on ledges and recorded alarm calls all failed. In 1954, The Goon Show devoted an entire episode to parodying the futile efforts to move the London roosts.

  The United States took the opposite approach. Starlings are exempt from the Migratory Bird Treaty Act, and no permit is needed to kill them. After research began in 1966, the chemical DRC-1339, now sold as Starlicide, best met the criteria. In 2008, the government poisoned, shot or trapped 1.7 million birds, more than for any other nuisance species. The 2005 US population was around 140 million, roughly 45% of the world total.

  Not every human use of the bird is hostile. In some Arab countries, starlings are trapped for food. The meat is tough, so cooks casserole it or turn it into pâté. One recipe says to stew it "until tender, however long that may be."

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