Why we love sparrows
In rowdy garden mobs or opportunist urban gangs, sparrows have thrived for centuries alongside people. But being our companion has come at a cost.
Living alongside humans has its ups and downs for these passerines
The din of playtime in the village school is audible way over the surrounding fields – a cacophony of shrieks and chatter, like a zoo with the primate enclosures inadvertently left open. The bell rings and the inmates are shepherded behind closed doors. And yet an echo of their clamour continues. From a dense hawthorn and beech hedge, a similar number of small voices is issuing a torrent of chips and chirrups, continuous as the rattle of pebbles in a stream. No one is waiting their turn, everyone is shouting at once… until they sense my approach, when it’s as though the headteacher has appeared – a sudden, guilty hush. I inch closer and the hedge erupts. A blur of brown bodies and whirring wings explodes up and away, heading for another favoured hangout where they can resume their rowdy conversation undisturbed. These are house sparrows, Passer domesticus – a species named in both English and Latin for its defining ecological trait: in almost every part of the world where it occurs (currently six continents, by far the largest distribution of any wild bird), it does so only where there are people. Largely, house sparrows are what ecologists call ‘obligate human commensals’, wild creatures that cannot thrive without us. Much the same is true for our other native sparrow, Passer montanus, the tree sparrow.
Crop chompers
The association between sparrows and people goes way back, beginning with the birth of farming in Eurasia, when early civilisations began experimenting with primitive crops: rice in China around 7000BCE, wheat and barley in the Levant as far back as 9500BCE. The small grains of these early varieties, grown and stored more densely than any natural seeds, were perfect sparrow food. The ancestors of today’s house sparrows spread west with the cultivation of wheat, tree sparrows went east, where rice was the main crop, before spreading back into Europe.
In time, both species found further opportunities beyond the fields and grain stores. House sparrows became particularly dependent on the feed given to horses and chickens, a resource that allowed them to thrive in cities as well as rural areas. The multi-species association between house sparrows, humans and livestock is so emphatic that when in 1957 the caretaker of Hilbre Island, a speck in the estuary of the Cheshire Dee, swapped his horse for a motor vehicle and stopped keeping chickens, the island’s breeding house sparrows disappeared. They returned a decade later when a new caretaker brought both horses and chickens back. The island is now a nature reserve, a haven for other bird species,
but uninhabited by humans, and despite being connected to the mainland at low tide, the observatory records no more than a handful of visiting house sparrows in a year. Similar declines occurred as other tiny UK islands have been more or less abandoned by people – South Havra in Shetland, Ynys Enlli (Bardsey) in North Wales and Rathlin, Great Blasket and Inishkea off the island of Ireland.
The ranges of house and tree sparrows now overlap extensively. On the face of it, the co-occurrence of two such similar small, seed- and grain-eating, cavity-nesting species seems to defy the principle of competitive exclusion, where ferocious rivalry would ultimately doom one species. The answer is in specialisation on a super-local scale. So, in areas where both species live, house sparrows tend to dominate in urban, suburban and village settings, while tree sparrows claim surrounding woodlands, farmland and parks. In my garden, for example, surrounded by woodland and mixed farmland, only tree sparrows visit the feeders. In a terrace of houses a few hundred metres up the road, and in most local villages, there are both, while friends 10 miles away in suburban York rarely see a tree sparrow.
Where house and tree sparrows live in very close proximity, they divvy up the available resources. For example, when it comes to nest sites in buildings, house sparrows prefer roof spaces, while for tree sparrows the nearest thing to a tree hole is a wall cavity or other crevice in a vertical surface. While house sparrows require a hole 32mm or larger, their slightly slimmer cousins can access spaces with an entrance 28mm wide, and thus aren’t excluded entirely from a breeding habitat. Tree sparrows may even modify the entrance to a nest hole to make it smaller and deter house sparrows. These slight differences are important from a conservation angle too – if you want to help both species on your patch, you’ll need to install nest boxes with both 28mm and 32mm holes.
Boom years
The concept of sparrow conservation would have seemed absurd to many a century ago. In his 1896 Dictionary of Birds, ornithologist Alfred Newton dismissed the house sparrow as “far too well known to need any description”. Even the British Trust for Ornithology, when launching the UK Common Bird Census in 1962, explicitly instructed respondents not to bother recording house sparrows, and only began counting them in 1976.
The sheer abundance of sparrows, and their ability to exploit us, made them the subject of ruthless control since at least Tudor times, with bounties being offered in rural parishes. Efforts ramped up in the 18th century as the easy pickings around expanding grain stores boosted sparrow populations. By the 1800s, a dozen sparrow
Where house and tree sparrows live in very close proximity, they divvy up the available resources.
‘Sparrow clubs’ tried to kill as many birds as humanly possible.
heads could earn a farm worker up to six old pennies – a valuable income. And the killing was intense: many parishes paid out for more than 10,000 dead birds a year, decade after decade, and some of these were areas of less than two hectares (two rugby pitches). During the late-19th century, rural communities formed ‘sparrow clubs’, not through admiration of the birds or academic interest, but with the explicit intention of killing as many as humanly possible. Club rules were generally simple: members undertook to kill an annual quota, with forfeits for failure to deliver and prizes for those who excelled.
Going gets tough
Perhaps the most startling thing about this centurieslong campaign is that it had so little impact. No matter how many birds were slaughtered, using traps, nooses, nets, limesticks, or by removing eggs, bird numbers rebounded. Sparrow reproductive strategy, like that of similarly successful commensals the house mouse and brown rat, involves a long breeding season and the ability to rear several broods in a year. This is an adaptation to cope with massive losses of juveniles, and because most of the control took place around harvest, the vast majority of the birds killed were indeed young.
The most extreme persecution was meted out in China as part of Mao Zedong’s self-styled ‘Great Leap Forward’, starting in 1958. Mao made eradication of what he perceived as major pests a matter of duty for the rural population. Sparrow nests were destroyed and flocks were netted, shot or harassed, with gongs and cooking pots banged with spoons until the birds died from exhaustion. The death toll ran to hundreds of millions, possibly billions, but the tragedy was compounded one year later when harvests across China failed catastrophically. The sparrows, as hastily-commissioned research showed, ate far more insects than grain – in particular locusts, whose numbers soared with the reduction in predation. The famine that followed Mao’s horrendous act of environmental vandalism cost the lives of some 25–40 million Chinese people. The numbers of tree sparrows, on the other hand, steadily rebounded.
Modern menaces
The extraordinary historic resilience of both tree and house sparrows makes what has happened more recently almost unbelievable. Declines in house sparrows were noticed first in large cities in the early to mid-20th
century. In the US, the species had become a ubiquitous alien by the time zoologist WH Bertgold wrote about what he called ‘English’ sparrows in Denver, Colorado in 1921. He linked a rapid decline to the replacement of horse transport by motor vehicles. Urban house sparrows in Britain suffered a similar decline, though the species remained abundant in rural areas.
More serious declines began to be noticed in the second half of the 20th century in the US and in western Europe, but nowhere were losses more noticeable than in London, where records suggested a collapse of 60 per cent between 1994 and 2004. The change was so sudden and so noticeable that questions were asked in Parliament, and a reward of £5,000 was offered by
The Independent newspaper to anyone who could come up with a convincing scientific explanation. That prize has never been claimed, but several ideas emerged.
In London, sparrows faced a resurgent predator in the form of urban sparrowhawks, which had increased from almost zero. Meanwhile, the steepest decline in sparrow numbers coincided with the removal of lead from petrol in 1988 and its replacement with additives, including methyl tertiary butyl ether. How this might affect the birds or their prey is not yet clear, but the theory fits with the fact that the fastest declines were in the places with the most traffic.
As well as this, rapid declines in insect numbers, as a result of pollution or insecticide use, and the elimination of nectar-rich ‘weeds’ from urban green spaces, must have made it harder for parent birds to provision their young. The decisive factor, however, may be disease. Rates of infection with avian malaria were recently found to be very high in urban house sparrows, and while the disease is not necessarily fatal, it probably takes a greater toll on birds already struggling with other pressures.
Species under siege
Sparrows in the countryside face problems too: tree sparrows declined by 93 per cent in Britain from 1970 to 2008. Their slump is easier to fathom. As farmland specialists, they have suffered disproportionately from agricultural intensification, including increased use of insecticides and herbicides, loss of scrub and hedgerows and more efficient mechanised harvesting, along with limited nest sites and year-round sowing that leaves a dearth of seed-bearing weeds. As environmental journalist Michael McCarthy pointed out in The Independent, “Mao didn’t need millions of villagers banging pots and pans; he could simply have borrowed the Common Agricultural Policy of the EU.”
It’s not hopeless. The loss of these once-familiar birds is deeply felt, and the problems that have been identified are solvable. Less polluting transport, and making space for unruly nature in both urban and rural environments, can undo much of the damage. And what serves to help sparrows will undoubtedly help other wildlife, too. So, if you hear that noisy chatter in a hedge or park or garden, take heart. It is a sign that something is going right.
AMY-JANE BEER is a biologist and author. Her latest book is Sparrows (Bloomsbury, £12.99).
FIND OUT MORE House sparrow facts: rspb.org.uk/birds-and-wildlife/wildlife-guides/ bird-a-z/house-sparrow