‘If a tree is felled in a large forest and nobody is around to hear it, does it make a sound?’ has been a philosophical thought experiment, since George Berkeley posed it in his 1710 treatise, highlights Iain Robertson, and much the same applies to guano!

Only once, while driving along the River Clyde coast road, at Greenock, west of Glasgow, have I heard the sound of bird poop as it splashes heavily across the bonnet and windscreen of a car. It was disturbing, as much for its porridge-like consistency and immediate loss of vision, as the dropped from several metres accelerated height made me fear that the car was damaged somewhat. Upon stopping at the next petrol station to experience not only the nose-scrunched disdain of paying customers but also the herring enhanced odour of the gull gloop, I did my level best to remove the copious deposit, using the forecourt’s attendant water bucket and a manually wound handful of blue paper.

Bird guano, a description preferred by that practitioner of televisual natural history, Sir David Attenborough, is a nitrogen-rich fertiliser that also carries beneficial phosphates and potassium…none of which are any good for the motorcar, or the maintenance of its pristine paint finish. With respect to Berkeley, the philosopher, it is the silent assaults that can prove to be the costliest.



Volvo Cars had loaned me a lovely dark metallic-blue V40 estate model, as a long-term test car, during the mid-noughties. Having rattled-up some 25,000 miles on it over the course of a year, it was scheduled to be uplifted from my domestic driveway that summer. With other vehicles parked on the gravel, it had been manoeuvred to a convenient, out-of-the-way parking space just beneath a sturdy black cherry tree. When I returned from four days away, attending various new model launches, I was mildly surprised to see the immense amount of fruit-coloured birdy poo, complete with shrivelled stalks, cherry stones and assorted discarded leafery cladding its bonnet and roof. I realised that urgent attention was necessary.

Whisking the car to my local Latvians, the high-pressure jetwash removed most of the solids from the Volvo’s upper surfaces. Yet, the manager of the hand carwash premises was most dismayed to inform me that, despite intense manual labour, using cutting compound and other paint/lacquer treatments, the fruit acid that the windscreen of the car had resisted so valiantly had eaten its way beneath the lacquer to damage the paint beyond repair. The car was collected by Volvo a day later; although no invoice was presented, I did offer to pay for the new bonnet and roof panel that Volvo’s loss assessor deemed necessary for subsequent sale. The cost was well over £3,000!

While I should have known better, the lesson was learnt. When bird poo lands on my car, an inevitability in an enclosed settlement with allocated parking bays and overhanging trees, I set to with hot water, cleaning cloths and applying polish to the paint finish. As so many of us have been playing the ‘isolation game’ of late, using our vehicles only when absolutely necessary, the impact of bird deposits, which are impossible to counteract by equipping wood pigeons with tiny diapers, can be manifold and disastrous.

Bird poo on cars

Bird poo on cars

While getting struck by bird poop may be perceived as a sign of ‘good luck’ in many countries, clearly another Sino-assault on our sensitivities, bird poop landing on the car does weigh-in a downside for its paintwork. Incidentally, I do recall wearing a brand new and most stylish leather jacket on a visit to Robin Hood’s Bay, on the North Yorkshire coastline, when a gull, which I presume was local and not necessarily a relative of the same rascal that sprayed my car in Greenock, delivered a reeky dose that rendered the fashion item unwearable thereafter. If you own a convertible, raise the roof.

Ford Motor Company actually tests its vehicles for this precise eventuality, with the able assistance of artificial bird poop. Developed by scientists, the droppings can be tailored to reflect the dining preferences of several avian species, adjusting a range of ingredients to reflect seaside diets, city-based culinary contents and the more natural detritus consumed by countryside corvids. From oleaginous to high acidic, most of the birdlife in Europe is catered for.

The concoction is applied to test panels as a spray, with sample pieces being aged at 40°C, 50°C and 60°C in an oven, to replicate the different applications in extreme heats, thereby also pushing the paint corrosion protection to its blinding limits. Ford’s ‘bird poop test’ is just one of the ordeals through which paint samples are put. The company also sprays phosphoric acid mixed with soap detergent and synthetic pollen on panels before aging them in ovens at 60°C and 80°C for 30 minutes. This test guards against damaging airborne particulates, like pollen and sticky tree sap, which you can feel are coating your vehicle’s paintwork, should you run your fingertips lightly across the panels.

IMGBy fine-tuning the pigments, resins and additives that go into making a car’s shiny protective paintwork, specialists can ensure that the coating Ford applies to its vehicles has the optimum constituents to resist the impact of most types of pollution. While bird poop is often white and black, it is not all ‘solids’. The white part is uric acid (a bird equivalent to urine) excreted simultaneously. The advice given to any vehicle owner not wishing to devalue his fast-depreciating asset is to wash down the affected area using warm water and a neutral pH car shampoo (never dishwashing fluid, which contains salt!). Remove the num num and apply car wax to restore the gloss.

Conclusion:       While Covid-19 is restricting our movements, it does not stop us from cleaning our cars. If you wish to avoid the most damaging impact of bird droppings, let alone sap and pollen, a decent domestic driveway valet might be precisely what the doctor would prescribe.