Bird Droppings

It’s over to my guest blogger today for some fascinating facts on this subject:


Today I thought I would take a break from the more serious subjects I’ve covered recently. The topic today is bird droppings (or more commonly pooh). Unsightly mess? Spoils public buildings & many other structures – definitely. But how much do you know about it? Will you even carry on reading this because you think it’s boring and uninteresting. Tell you what – I thought that before I started thinking about it. It almost became something “to get excited about” as LLM might say.
I wonder if you’ve ever been hit by bird droppings from the sky as you walked along outside? I have. I was fortunate though, it landed on my shoulder (and therefore thankfully missed my head although it did get some small splashes) and left me with a stained shirt for the rest of the day. Yes, I was on my way to work walking from the train station. Oh well, it gave people in the office a good laugh when I arrived with the mess down the front. (“I see you had some visitors drop in on way to work this morning”, and other such witty remarks.)
So what could be interesting about bird muck? Well, in case you’re struggling, one of our national newspapers came to the rescue recently. It published a survey analysing droppings found on cars in different cities in the UK. It seems to suggest that it’s not just where you park your car that affects whether it gets muck on it but that it is related to the colour of your car. Is there a colour, for instance, which does or doesn’t seem to get hit as much as others? Yes there is but it’s not as simple as that. Before we go any further let’s look at the published table below:

Red – 18 per cent
Blue – 14 per cent
Black – 11 per cent
White – 7 per cent
Grey/Silver- 3 per cent
Green – 1 per cent

This is quite interesting as you can see that nearly 1 in 5 cars that are hit are coloured red. Hmm.. perhaps you won’t buy a red car next time. Before you get too carried away by this revelation just look at those figures again. Now you don’t have to be a maths whizz to see that the figures don’t add up to anywhere near 100%. I make the total 54% (and this is the full table as appeared in the newspaper). (You might have to add 7% if the white/grey means two colours tied on that figure but it doesn’t say.) What happened to the other 46% of the sample? Were they all colours different to the ones specified? If so why not include an “other colours” category? LLM covered “getting excited” about stuff but at this point I was doing “getting angry” (at the quality of this presentation). Why publish such a rubbish table which appears to show only just over half of the number surveyed? Is the paper really that bad at its adding up? (Is this turning into a “Chat 2” blast?)
Ok so let’s look at some more of the detail behind table. They looked at 1,140 cars across five cities: Brighton, Glasgow, Leeds, Manchester and Bristol. Sounds like a fair spread, north, middle & south, but wait a minute, think about this – why no London investigation? (London is noted for its population of pigeons in certain areas so should have been a good area to get a lot of test results.) Seems like a fair number of vehicles but did you know, as of the most recent figures, there are 31 million cars in the UK (and 134 million in the USA). Now take the sample size and divide it by the total number of cars (& times by 100) to get a percentage – any guesses? I’ll tell you it’s 1,140/31,00,000 = 0.00367% – that is 1/272 of 1%! Just take a moment to think about that – not half of 1%, not a quarter of 1%, not even one 100th of 1% or one 200th of 1% but 1/272 of 1%! How small is that? Now come on, since when did a fraction of 1% as small as that represent a big enough sample to make inferences about cars across the whole country. And yet, there in a national newspaper, the survey is given some column inches with no ref to how small the sample is when compared to the total number of cars on the road.
So far, amongst other things, we have: an apparently incomplete table that doesn’t add up to anywhere near 100%; we have a sample size so small that it makes it hard to deduce meaningful data; and we don’t know why the capital of the country has been excluded from the survey.
Steam is (metaphorically) beginning to come out of the ears at this point but bear with me there’s more.

The next bits are what I would call basic. Think about it – we are not told anything about the locations surveyed. Were the car parks on open ground? Were the cars just parked in streets? Were there overhanging branches or even road or rail bridges which often have metal support girders underneath providing many ideal perches for pigeons? (The car park at my own place of work actually has a dual carriageway going over it so has two bridges & therefore lots of girders & therefore lots of pigeons.)
Remember too that the research did not consider the type of birds doing the fouling of the vehicles. (They actually spelt it “fowling” at one point in the article – haha.) Whilst they could not possibly see all the birds doing the deeds it is possible that they surveyed at a place in a city where there is a resident population of a particular type of bird –pigeons, sea-gulls or starlings for example. Btw, did you know that pigeon pooh is more damaging than say seagull pooh? I’m sure you want to know why so I’ll tell you – it’s because pigeons eat seeds and therefore produce grainier pooh and it’s that which causes more blemishes on your car’s paintwork. However what about all those smaller size birds: sparrows, starlings, blackbirds, finches, thrushes etc?
The article also gives you the useful info, from car polish experts Autoglym, that car paint damage is NOT caused by the acid or alkali in the pooh which I always thought – so I did learn something useful from reading it. I won’t bore you with the technical explanation – if you’re really interested you can look it up.
Did you know that insurers estimated that the annual cost of damage to paintwork from bird droppings is about £57 million? Best advice? – just clean it off as soon as possible. Well I’d never have thought of that!
In the car park where I work two people have yellow cars. Why is yellow not in the survey table? Does this mean it’s the safest colour to buy because the survey did not spot one yellow car with bird muck?
Another stat which might have been helpful is the colour distribution of cars on the road. Supposing, for instance, that 18% of all cars on the road are red, it would be no surprise that 18% of the bird muck survey were found to be red cars would it? This again is basic stuff which any normal person would ask. It’s like saying that a survey found that the average age of people going into a particular building was say 68 and you say why so high? Why were there not more younger people going in? Ah well, you see, it’s a day care centre for pensioners. Bigger picture springs to mind here!
It takes about 3 seconds to research colours of cars sold. Here’s the table of colours of cars sold (so not the actual total in the country, but does include yellow) for most of 2010:

1: black Cars sold: 465,249 Percentage share: 24.7
2: silver Cars sold: 402,537 Percentage share: 21.4
3: blue Cars sold: 310,331 Percentage share: 16.5
4: grey Cars sold: 270,863 Percentage share: 14.4
5: red Cars sold: 192,335 Percentage share: 10.2
6: white Cars sold: 188,463 Percentage share: 10
7: green Cars sold: 20,735 Percentage share: 1.1
8: beige Cars sold: 17,237 Percentage share: 0.9
9: yellow Cars sold: 7,621 Percentage share: 0.4
10: brown Cars sold: 6,967 Percentage share: 0.4

These figures do come to 100%. Again simple bit of research – look at the top 3 in the bird dropping sample (red, blue, black) and add up the percentage figures. It comes to 43%. Now look in the table for 2010 sales and add up the percentages for the same 3 colours – it’s 51%. Not that far apart I’d say.

Inference – the more cars there are of a certain colour the more likely they are to get hit! It’s not rocket science but it doesn’t make headlines and you know as well as I do that “headlines” sell papers.
Another newspaper gave the following table apparently for most popular car colours IN THE WORLD! And here it is:
1. Silver – 26 percent
2. Black/Black Effect – 24 percent
3. White/White Pearl and Grey – 16 percent each (tie)
5. Red – 6 percent
6. Blue – 5 percent
7. Brown/Beige – 3 percent
8. Green – 2 percent
9. Yellow/Gold – 1 percent
10. Others – <1 percent
We see that this table also does add up to 100% (you do have to add 16% to the 84% total because two colours were tied in third place).
Black, red, blue comes to 35%. Not that far off 43% really.
Now, apart from the fact that I was “getting angry” about this terribly presented (bird droppings) survey, I was amazed to note what I had come to believe over many years was actually being confirmed. I have on a number of occasions come to my car to find it has droppings on and yet the one next to it has none. When it first happens you don’t notice anything special but when it keeps on happening you begin to wonder: am I parking under a bird’s nest? Is there a tree branch over the parking place? Did I definitely remove the “Pooh here” notice from the roof of my car? Ooh… wait a minute was the notice invisible? – remember “Invisible Art” from 4.7.12. Better check that.

Ok so now you know the facts but will it influence the colour of car you next buy. Will you rush to the research paper and get the info and then decide to buy a GREEN car or even SILVER?
And you thought bird pooh was not that interesting. (Maybe you still do after reading Mr Angry’s rant.) What about readers of this blog sending in the colour of their car and whether it gets “pooped on” on a regular basis.

Last word has to go to the Ornithology experts who were quoted in the article:

“The British Trust for Ornithology is more circumspect on the role of colour in the ‘drop zone’ for birds.

A spokesman said: ‘We do know that birds can be attracted to certain colours during display but droppings on cars are probably more to do with where you park; if you park where birds roost then you are going to get more droppings on your vehicle.’”

Incredible! Would you have thought of that? – and they didn’t even do a survey to back their conclusion up.



8 responses to this post.

  1. Ha ha.Pretty funny.


  2. Thanks keerthikasingaravel. Glad you enjoyed it. LLM is correct, I don’t have own blog but when she first started I asked if she would accept a guest blog and it started from there. When I feel something needs saying she will usually donate her Wednesday slot to me. (Thanks again to LLM for this.) I like to think of it as a kind of “Wednesday Wisdom” thing. Don’t know if you’ll find any pearls……. but I try.


  3. Oh my gosh, I can’t believe someone studied that. We have tons of geese around here right now and they go all over in the street!


  4. […] “boys” or “girls”. I’ll bet she shop lady is not popular with the car owners. Remember the post about bird droppings; the birds are standing on a silver car and silver formed only 3% of car colours which get hit. […]


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