Across the land, particularly in urban areas, the chirping of sparrows falls silent in the concrete canyons of our cities, and indeed the great cities of Northern Europe [
1 ,
2 ]. Something is doing for our house sparrows, and we don’t know exactly what it is.
tribulations of science in the city – the difficulty of isolating the variables in urban habitat changes
what’s up
Kate Vincent has studied the sparrows’ plight and her PhD thesis
shows that later broods are dying in the nest from a lack of insect food.
It is difficult to establish, however, what this is due to. The House sparrow, as its name indicates, is closely dependent on the human environment, it may be that changes in the built environment are what is making food scarcer. This would tally with the observation that the percentage decline is highest in large urban areas such as London, and less on farmland and towns.
the why
It may be that something else is reducing the number of insects in the urban environment. Or that the number of insects is the same, but the sparrows are finding it more difficult to locate or catch them. Kate Vincent’s findings do, however, point out something that can be done to try and reverse the decline locally – feeding sparrows mealworms in the breeding season,
as in this studyIt is naturally important to try and find out why there are fewer bugs in our cities. Perhaps we have been too good at killing them off with pesticides, but there is one obvious change in London’s leafy suburbs since the end of the 1970s. They became a lot less leafy as the decades passed. Insects don’t normally feed on concrete, so it stands to reason that there are a lot fewer insects about!
urban habitat changes – paving sparrow paradise
Let us reflect on the changes in the urban residential environment over the years since the 1970s. The postwar social housing model with its even frontages and miles of privet hedges was dismantled by the Thatcher administration in the 1980s giving tenants a right to buy. This dramatically raised the level of home ownership, which in British society is generally considered A Good Thing. As the years rolled by, owner occupiers new and old increasingly owned cars, and many of Britain’s houses were not designed with car parking in mind. This started a trend in the 1990s that we are about halfway through, where many front gardens are paved over for parking.
As well as becoming more numerous over the years, cars have become much bigger with the increased popularity of people carriers in the late 1990s and now a general trend to 4×4 and sports utility vehicles. Previously, parking was often achieved with a couple of parallel strips of concrete set into the original grass, but this is not longer adequate. Complete paving is often selected since the spacing of a saloon car and a 4×4 wheels aren’t the same, and garden maintenance is reduced. Techniques exist now to concrete over a front garden in half a day using a cement mixer to pour on site and another machine for format the concrete into faux paving.
Other incentives add to the pressure on the humble patch of grass and hedge that made our suburbs earn the adjective ‘leafy’. Insurance companies often offer discounts for off-road parking, and some councils started to charge for residents’ parking permits in the 1990s for urban homeowners to park vehicles on the road in front of their houses.
All this of course reflects increasing wealth, home ownership and mobility which are good things in themselves. However, one outcome is that there is far less greenery in the residential environment. On a recent survey of an area of town with no original car parking half the front gardens had been paved over. With these gardens goes the vegetation that provided seeds and insects, and the hedges that provide sparrows with shelter, and formed wildlife corridors along which sparrows could travel in relative safety.
In addition to the pressure on the general greenery of the urban ladscape, modern roofing methods reduce nesting opportunities in the classic sparrow’s nest position in the eaves of the roof. The roof space becomes inaccessible and the number of gaps that appeared over time as wood warped is reduced.
It is difficult to analyze these changes in the habitat on a sound scientific basis. Changes in the built environment happen piecemeal as the result of many independent individual decisions. The changes are poorly documented – plannning permission isn’t needed to convert a front garden to a concrete carpark. It isn’t easy to separate the variables and establish controls – the loss of one garden and hedges is unlikely to affect the local sparrows, but the loss of half of them will. Putting them all back and testing if things get better next year isn’t an option.
The weakness of the scientific method is that what cannot be measured analytically shows up less in the analysis, but it is not necessarily irrelevant in this case. Most other habitats are more amenable to leaving one area alone which changing another, but the urban residential environment, with its patchwork ownership is particularly difficult to control. It is exactly this environment that the house sparrow has chosen as its preferred habitat. And it is exactly this intractability of this environment to scientific analyisis which means that the reason why the “cockney sparrer” has sounded the last chirp across the nation’s capital may be discovered too late to forestall the last chirp ringing out across our market towns over the next few years.
The
BTO study used the alternative approach of taking the patchwork built environment as it was correlating sparrow numbers with the fragmented habitat. This showed a dependence of nest sites, and a dependence on nearby greenery, supporting the habitat hypothesis to some extent. However, the habitat was already fragmented – it is a pity that results aren’t available from the early 1980s as a control. It is also puzzling that the decline is not evenly spread – Berlin for instance has not suffer a sparrow decline as yet. Anybody who has been to that city will not fail to have noticed it has a lot more greenery in its wide avenues that say London or Paris.
failing sparrows in their hour of need
The scientific method has helped our bird organisations to greatly improve nature reserves, studying what works, and optimising their limited resources to greatest effect. Where it is possible to control the vast majority of the variables, establish control populations or roll back changes experimentally, the scientific method is the best and fastest method to optimize results.
However, science may yet fail the house sparrow in its hour of need, because of the difficulty of applying it to the sparrows’ chosen habitat. This seems to be delaying the formulation of any response. One aspect of that response could be to remove the financial pressure to introduce potentially sparrow-unfriendly (and somewhat human-unfriendly) changes like paving over the grass and remove hedging in front of many suburban homes. There is a difference between making costly changes to an environment without a sound scientific basis, and ceasing to subsidize changes which are probably sparrow-unfriendly, though as yet not proven scientifically. The science basis of the bird organisations is right where expensive action is needed for something that would conflict with many people’s interests. A far lower standard of proof is acceptable to simply cease encouraging the dismantling of the sparrows’ habitat and food supply.
Controlled parking zones may well still have their merits, but actually charging the council tax payer to park in the street is perhaps not the best way to go. In the end the built environment needs to serve its human population more than its sparrows. We may come to the sad conclusion that our thirst for concrete to park our sports utility vehicles is going to destroy our city sparrows. We may wish to spare a thought for how we may give some of our sparrows safe havens. If it means scattering nestboxes across our Royal Parks or keeping horses in an area – even allocating an area of derelict buildings to sparrows, then we should consider it.
The incessant chirp of the cock sparrow does not have the resonant beauty of the nightingale or the mellifluous tones of the blackbird. His chirp is nevertheless a spark of life holding sway against the mechanical loneliness of the urban environment. He has travelled a long way with us, our cock sparrer, and now our needs and his diverge. Let us spare him a thought, and ask ourselves whether it really means nothing to us that we now drive this cheery fellow traveller from our city environment.
It is not just the humble sparrow that would gain from slowing the switching out of leafy greenery for patterned concrete. We humans too might prefer to see softened greens of the trees and hedges rather than the grey concrete. There’s a balance to be struck here, and tipping the balance away from concrete would make a better world for us and our sparrows.
Sparrows Leave the citiesRIP Cockney SparrowRSPB Save the house sparrow initiativeBid to save sparrows launchedLabels: last chirp, sparrow
