Inheritors of the Earth

by Chris D. Thomas

  The occasional intrepid Bactrian sparrow is drawn away from this tough landscape in search of easy pickings. They can be spotted stealing grain from local stalls in Kazakhstan’s Baikonur market during the summer months, and from the small Indian village markets that dot Rajasthan’s landscape in winter. And this may be how it all started. Somewhere in the swathe of land that today encompasses northern India, Pakistan, Iran, Iraq and westwards to Syria, wild sparrows much like the present-day Bactrian sparrows must have started to find it easier to find food by hanging around the villages that sprang up in the fertile valleys where agriculture first developed. The large and tasty grass seeds–progenitors of wheat–that our ancestors cultivated would have been enticing. Rather than glean small, scattered seeds from the steppes and semi-deserts of western and southern Asia, why not head into town and stuff your crop from a large pile of big fat grains? It is easy to imagine that these bloated individuals might have survived better, and then have been able to raise more chicks than their wilder ancestors. And if the villagers were also making new earthen banks with cracks in them–the walls and roofs of their houses–then why not nest in them rather than fly miles away in search of natural crevices? So it must have been that a group of sparrows gradually abandoned their wild existence, maybe ten thousand years ago, and moved into our villages and towns. They have been our companions ever since.

  Its destiny sealed, the sparrow spread around the world from its origin in Asia, moving to wherever we built houses, spilt grain, left bags of food unguarded and deliberately threw out our scraps for them.1 The wild grey-headed sparrows, with streaked orange-brown and black wings and creamy-grey breasts, whose appearance allowed them to merge into the brownscapes of western Asia, entered our homes and became the familiar house sparrow. These new domestic sparrows remain the same biological species as the truly wild birds that still fly out over the Asian steppe in search of insects and seeds. In some respects, they are unchanged. They continue to pursue insects for their young (often in our yards and fields) and seek out grass seeds (which we call cereal grains) for themselves. They are still living in grey-brown places: our towns–it just turned out that the conversion of the world into a land of farms, villages, towns and cities made the whole world just a bit more like their Asian homeland. They got lucky.

  The house sparrow conquered Asia and Europe thousands of years ago, eventually coming to inhabit villages and towns from Portugal in the west to China in the east, and from Sri Lanka in the south to Norway in the north. The familiarity of Ancient Egyptians, Greeks, Romans and Indians with them attests to the long period over which sparrows have been integrated into the human world. They became part of human culture: they were sacred to Aphrodite, the Greek goddess of love, and their exuberant and public copulation led the Indian scientist Varāhamihira to admire the sparrow’s virility in the sixth century. Others interpreted their behaviour as vulgar. Sparrow hieroglyphs denoted a sense of being bad and small to Ancient Egyptians. St Matthew’s gospel related how sparrows were regarded as of such low value that two would be sold for a single Roman assarion coin.

  Somewhat more recently, Queen Elizabeth I’s 1566 law classified sparrows as vermin and placed a small bounty on each bird in England. In the eighteenth century, the sparrow was the nursery-rhyme villain who killed cock robin with his bow and arrow. Hymn writer Civilla Martin composed ‘His Eye is on the Sparrow’ in 1905 to explain how, if the Lord’s munificence stretches as far as the insignificant sparrow, he surely must care for any human who would sing his praises. Humans have had a love-hate relationship with the house sparrow for at least five thousand years, and probably for ten thousand.

  Having completed its European and Asian adventure, the sparrow was then thwarted, bounded by the Atlantic Ocean to the west, and by the Indian Ocean and the Sahara Desert to the south. These distances were too far to fly. If it was to follow the burgeoning world’s human population elsewhere, it needed help. Fortunately, it was at hand. In the nineteenth century, New Yorker Eugene Schieffelin embarked on releasing–in North America–every different kind of bird that was mentioned in the works of William Shakespeare. To help achieve his aim, Schieffelin argued that ‘English’ sparrows, as they had by then become known, would help control insect pests in the New World. So they were brought to North America to get rid of a ‘plague’ of caterpillars of the snow-white linden moth on no stronger evidence than that sparrows sometimes eat caterpillars. They failed to control the caterpillars and instead mainly consumed dropped grain, human food scraps, and seeds that could be excavated from the piles of horse dung that adorned the streets of New York City at the time. They were released in at least a hundred towns and cities across thirty-nine American states and four Canadian provinces between 1851 and the end of the 1880s.2

  The house sparrow has a contrasting grey crown.

  The Italian sparrow’s crown is brown and it has a neater chin.

  Tree sparrows clearing leftovers off plates in a jungle lodge at Danum, in Borneo.

  Tree sparrow with its dark cheek patch.

  Seeking out scraps on a feeding station for proboscis monkeys. House sparrows originated in Asia and are now spread throughout the world, associated with humans. Tree sparrows are also found in Asia, but have become the urban and village sparrow of tropical Southeast Asia; another human-associated success story. Italian sparrows did not exist before humans developed agriculture and towns. They originated when house sparrows spread out of Asia and hybridized with Spanish sparrows.

  Sparrows were also introduced to Cuba and Argentina in the 1800s and quickly spread through the Americas. They were released in Australia and New Zealand, and brought to South Africa and Zanzibar, from where they colonized most of the other countries that lie to the south of the Sahara. They even made it to remote islands across the Pacific, Indian and Atlantic Oceans, sometimes intentionally, sometimes as stowaways. The house sparrow became a true world traveller. A fairly localized and apparently quite unexceptional russet brown, buff, black and grey bird that lived in the grassy plains of Asia has become one of the Earth’s most widespread species, relying on humans to provide it with transport, food and homes. It is one of the most successful species in the world: inheritor number one of the human-altered Earth.

  The close association of humans and sparrows continues to the present day and still generates the age-old mix of fondness and irritation. My childhood education in coarse language was provided by my father’s guttural curses as he cleared sparrow nests that were blocking our house’s down-pipes; a mass of dry grass, feathers, horsehair, paper and baling twine showered me as I steadied the ladder. Dad found sparrows distinctly irritating, and he would have been delighted that there are only a third as many house sparrows in Great Britain today as there were on that summer day of 1967 when we cleared the eaves. But conservationists and concerned citizens are seemingly on the side of my seven-year-old self, who liked having sparrows nesting in the roof. They want to protect sparrows, even though British house sparrows actually stopped declining around about the year 2000; there are still over 10 million of them in Britain, not to mention half a billion in the world.3 The house sparrow is one of the most widespread animals on our planet and, if we are to be rational about spending limited conservation budgets, one of the species that least needs our help. This concern for house sparrows is doubly odd because conservationists tend not to look kindly on foreign species–and there would be no house sparrows at all in Britain had it not been for the fact that humans created somewhat steppe-like conditions in the Home Counties. But sparrows arrived long enough ago that we have apparently declared them to be a ‘native species’ that needs protection. Researchers funded by government, conservation organizations and universities have been spending time and money to diagnose the ‘problem’, which implies that the preferred state of Britain is to have even more sparrows. More precisely, because the justification for the work is the two-thirds decline between the 1970s and the year 2000, the ‘correct’ numbe
r of house sparrows is taken to be roughly how many there were in the 1970s. Picking any specific date is obviously completely arbitrary. Choose a start date of ten thousand years ago, and the ‘correct’ number of house sparrows in Britain would be zero. Not to be put off, the recent surge in enthusiasm for sparrows has even been incorporated into an updated 1981 version of English law, which aims to protect all wild birds. In the second Elizabethan age, it is illegal to kill or injure sparrows intentionally, or to remove any of their nests that are in active use.

  This research has revealed that the late-twentieth-century decline likely stemmed from a reduction in the amount of dropped grain and weed seeds, insufficient insect food in urban areas to provision their chicks, and perhaps also from an absence of suitable crevices for the birds to use as nest sites in modern buildings.4 Cleanliness leads to fewer sparrows. The solution was obvious: feed the birds. The bird-feeder business is booming and people have even started putting out trays of expensive mealworms (beetle larvae) so that sparrows can supply their insect-deprived chicks with protein-rich meals. Concerned citizens and local councils have begun to install human-made breeding cavities. You can purchase conventional wooden nest boxes, 3D-printed ones, or hollowed-out bricks that provide nesting sites in the walls of your house and three-storey sparrow houses to provide safe havens. The love that humans have for sparrows seemingly has no end.

  But the hate continues too. A century ago, the professional writer and lecturer William Dawson, no fan of Eugene Schieffelin, described the introduction of the English sparrow to the United States as ‘the most deplorable event in the history of American ornithology’.5 While European researchers and conservationists try to increase the numbers of sparrows, their North American counterparts contemplate the reverse. You can order sparrow-proof nest boxes and ‘Deluxe Repeating Sparrow Traps’ online. No doubt it is a profitable business selling anti-sparrow devices to concerned citizens wishing to oust unwelcome foreigners, and pro-sparrow feeders and nesting boxes to their neighbours who would welcome them in!

  In America, sparrows stand accused of evicting beautiful native bluebirds from their nesting holes, and even of killing them. As the Michigan Bluebird Society put it: ‘House Sparrows are an overly aggressive, alien species of bird that prefers similar habitats and nesting locations as bluebirds. The male sparrow is particularly nasty and will often kill not just the young bluebirds but even the adults and eggs too. House Sparrows MUST be controlled in the habitat your nest boxes are placed in to ensure the nesting success of bluebirds.’6 This sounds dire, but the prize is great–the protection of bluebirds. With their brilliant cobalt-blue backs and heads, rusty-red chins and chests and downy, cream bellies, bluebirds are stunning creatures indeed. But should we really inflict capital punishment on sparrows for the horrors that they inflict on luckless bluebirds?

  If we care about the future of bluebirds, we first need to know whether bluebirds are declining, as many conservationists have claimed, and whether sparrows are the cause. American naturalists have been counting bluebirds and other native species using standardized methods as part of the Audubon Society’s Christmas Bird Counts since 1900, and counts of sparrows commenced in 1951. Their records tell a tale that is not consistent with the fear-mongering of the pro-bluebird, anti-sparrow lobby. Oddly, sparrows have declined by some two-thirds since 1951, just as they have in Britain (probably for similar reasons), while bluebirds have increased by nearly a half.7

  Closer inspection of the Christmas Bird Counts shows that year-to-year changes in the numbers of bluebirds are not affected by the numbers of sparrows, and year-to-year changes in the numbers of sparrows are not affected by the numbers of bluebirds either. The fact that the number of bluebirds increased while that of sparrows decreased (although they remain more numerous than bluebirds) between the 1950s and the 2000s appears to be coincidence, no different from the chance of getting one head and one tail when tossing a coin twice. This is not surprising. Only a modest proportion of all evictions of bluebirds from their nest sites, and a very low fraction of all bluebird deaths, are likely to be attributed to sparrows, given that most bluebirds live in rural locations, where they benefitted historically from humans clearing the original forest and opening up the countryside. In recent years, they have also benefitted from the deployment of bluebird nest boxes, and this may well have contributed to increased numbers in some areas.8 If we consider the last two centuries in the round, both these bird species have taken advantage of living alongside humans.

  So why have sparrows been unfairly blamed for the imaginary decline of bluebirds? Why do we not equally hate all the native North American animals–including tree swallows, flickers, hawks, chipmunks, squirrels and raccoons–that also evict or kill bluebirds? While it is true that sparrows are guilty as charged of killing some bluebirds, so are our pet cats. Is the reason simply that sparrows are clad in dowdy browns and greys and bluebirds are clothed in appealing iridescent reds and blue, or is it because sparrows are, as the Michigan Bluebird Society put it, ‘alien’?

  When it comes to conservation debates, it often seems as though we have set ourselves apart to act as referees and arbiters of how nature should be–yet our stance lacks consistency. There is no correct state of nature. In Western Europe, we have declared house sparrows to be native and desirable, even though house sparrows live in the region only because humans created the towns and farmland they thrive in. We apparently want to have even more individuals of a species whose numbers already run into the hundreds of millions across the world. Why not just be happy with the numbers we have? They would not exist in North America either without humans–there they are treated as alien and potentially harmful. The desirable state of North America is apparently to have fewer sparrows, or none at all.

  The story is more or less the same on both continents, separated by a few millennia, but we have come to diametrically opposed opinions. Faced with one of the biological inheritors of the human-dominated world, we are left in a quandary that leads to different reactions. Yet this is the world we now inhabit–one that contains winners as well as losers.

  Later in the same summer that my father and I evicted sparrows from the eaves of our family home, I found myself inspecting a bird that was sitting next to me on a stone bench in St Mark’s Square in Venice. Ignoring my familial duties, which were to admire stone arches and mosaic-filled churches and attend demonstrations of glass blowing, I turned my attention to Venetian sparrows. The sparrow in question was after my crumbs, competing for food with jostling crowds of feral pigeons–another biological success story. Proudly brandishing my first ‘child’s bird guide’, I set to the task of trying to identify it. It did not look quite like any of the illustrations, but my mother and I decided that it must be a rather unusual-looking Spanish sparrow on account of its rich-brown head. I was delighted to be able to add a new species to my list. When I consulted a more complete ‘adult’ bird book back home in England, I discovered that we were wrong. Under ‘house sparrow, Passer domesticus’, I found the following words: ‘Male Italian Sparrow… has brighter coloration in breeding plumage, with rich chestnut crown, whiter cheeks and under-parts’.9 There it was, exactly what we had seen–an Italian sparrow. Back in 1967, I was cross that I had to remove ‘Spanish sparrow’ from my list of birds, and even crosser that I could not add ‘Italian sparrow’ instead. According to the book, it was a type of house sparrow.

  What I did not know as I watched that Italian sparrow pecking at the fragments of the Milan biscuits that I had deliberately dropped was that the sparrows themselves held the secret to their origins in their genes. Just as the genetic ‘fingerprints’ of humans have on occasion been used to identify the true biological parents in cases of disputed inheritance, the ancestors of species whose origins are disputed can also be analysed. In this case, it should be possible to tell whether Italian sparrows are most closely related to Spanish sparrows or to house sparrows. To find out, nearly fifty years later I set off to visit
a group of sparrow geneticists. My route took me through Oslo’s Frogner Park, past a few more of the world’s half-billion house sparrows and quarter-billion town pigeons, all enjoying a day of October sunshine. They were picking up scraps from human visitors who were there to see the life’s work of the sculptor Gustav Vigeland, a man seemingly obsessed by curvaceous nudes. Eventually, I located the University of Oslo and the building that houses the renowned Centre for Ecological and Evolutionary Synthesis. The door was open, so I just walked in, past cabinets filled with the stuffed bodies of zoological specimens. With no reception to be seen, I carried on, wandering down poorly signposted corridors. Eventually, I arrived at the door, knocked and entered. There I met the guitar-playing, curly-haired Glenn-Peter Sætre, my former student Richard Bailey and several of their colleagues.10 Glenn-Peter had put together a veritable army of sparrow geneticists, who had set about trying to uncover the history of the house sparrow and the genetic origins of the puzzling Italian sparrow.11

  They discovered unique genetic sequences, some of which could only be found in Spanish sparrows and others only in the house sparrow–clearly these two were separate species. This was interesting, but not that surprising. The house sparrow had developed in Asia, while the Spanish sparrow lived predominantly in Europe. The surprise came when they analysed the Italian sparrow. The Italian sparrow, it turns out, contains a good old mixture of both Spanish and house sparrow genes. The only logical explanation was that they were hybrids. Glenn-Peter and his colleagues suppose that, as the house sparrow followed the development of villages and agriculture and spread out of southern Asia some thousands of years ago, it met up with the Spanish sparrow. Despite its modern name, the Spanish sparrow lives throughout the Mediterranean region and is not confined to Spain–it must have been found in suitable places in parts of the Italian Peninsula before the house sparrow turned up. It transpired that the hybrids between these two types of sparrow were fertile, and the Italian sparrow was born, with its chestnut-brown cap and white eyebrow borrowed from the Spanish sparrow atop the livery of a house sparrow. A new genetic race had come into existence.