In the previous blog I estimated the number of feathers on living wild birds to be around 420 trillion.
Now I’ve had the chance to check a few things I’d like to revise the estimate a little.
The logic strikes me as pretty good. How many (wild) birds are there in the world and simply multiply up by the number of feathers on a bird to get the answer.
How many feathers are there on a bird? This seems a good enough guide and suggests that my plucked (get it?) out of the air estimate of 5000 probably wasn’t very wrong.
How many birds are there in the world? If you Google that question you find an estimate of 200-400 billion which seems to be based on a bit of proper study. So I was on the low side, it seems, with my guess of 84 billion – although I feel pretty chuffed I was that close (and it took very little time).
So with 300 billion birds in the world, on average covered with 5,000 feathers, there are 1.5 quadrillion feathers. Well, who’d have thought it?
I like this type of mental exercise. It’s surprising how often one comes up with a final answer that is pretty close to what appears to be the right one. I remember driving from Cordoba to Granada once discussing with my son how many olives there were in Spain (we were driving past fields of Olive trees) – it passed the time pleasantly.
And we started with a seemingly intractable question – how many feathers attached to wild birds are there in the world? Easy to shrug and say ‘don’t know’ but it is a tractable puzzle. I have sympathy for anyone who says they don’t care – that’s fair enough.
PS And my UK guesses were quite good: there are 23 UK bird species with over a million pairs (I guessed 25 after thinking of 16 (all of which were right)) and my estimate of the UK bird population at 150 million was very close to the real number of 168 million (see here). I’m sure that these good guesses were partly luck but also partly having vague incoherent memories of the right answers swishing around in my brain which steered me towards something vaguely sensible.
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Some academic points on feathers:
Feathers (2012) by Thor Hanson counts as a very good read.
Feathers make birds count as a bit other – (some folks are a bit phobic touching birds).
Feathers are clever for recounting Tyrannosaurus-type stories.
Feathers are clever for sometimes creating the inexplicable urge to count them, thereby generating vast data to feed to half house-trained statisticians wielding terrifying formulae leading to – perhaps –
A Special Theory of Anorakivity
I like Murray M’s concept of a “Theory of Anarakivity”.
Definitely a theory that merits further exploration.
I can remember a chap asking my why I wasn’t going to kill a Sparrowhawk caught for ringing ” because it eats all the little birds”
I asked him how many young Blue Tits have he suggested 6. So I said and “all those tits moult their feathers once a year. Thus because they eat so many tits over the years Sparrowhawks are saving us from being smothered in several feet of moulted feathers.”
He did I think get the point.
I collect feathers or at least some feathers, my largest is a long primary from a captive Andean Condor, with a shaft as thick as one of my fingers and nearly 60 cm long.. Not sure about the smallest. The patterns on feathers are endlessly fascinating as is the structure..
I have a short-toed eagle feather that I watched falling from the bird as it passed overhead years ago in the Camargue. I noted where it landed and went to fetch it!
Memorabilia
BY ROBERT BROWNING
Ah, did you once see Shelley plain,
And did he stop and speak to you?
And did you speak to him again?
How strange it seems, and new!
But you were living before that,
And you are living after,
And the memory I started at—
My starting moves your laughter!
I crossed a moor, with a name of its own
And a certain use in the world no doubt,
Yet a hand’s-breadth of it shines alone
‘Mid the blank miles round about:
For there I picked up on the heather
And there I put inside my breast
A moulted feather, an eagle-feather—
Well, I forget the rest.
“I like this type of mental exercise.” Why?
This reminds me of someone I was at school with. Taking Einsteins theory of special relativity and length contraction he insisted on trying to work out how much a bus would change in size the faster it went.
I suppose it depends if you’re on the bus or not. Mind you, I always sit on the lower deck of buses because it keeps me younger. I’m now an estimated 2 billionth of a second younger than I would otherwise have been. Actually some scientists are these days quite interested in relativistic effects at this sort of scale.
In my youth I was taught
“Forty thousand feathers on a thrushes throat”
well it sounded something like that.
Given that one of the functions of feathers is insulation, is there any relationship between latitude and the number of feathers? Does a blue tit in Norway, for example, have more feathers than one in Belgium and does the Belgian one have more than a Spanish one? Or perhaps they have the same number but they get less ‘fluffy’ with decreasing latitude? (I appreciate that the number of flight feathers does not vary in this way!).
Jonathan, I think you might’ve answered this question when you suggest that the higher the latitude the more fluff (down) there is across all species of birds (ref: Thor Hanson, Feathers p 89). So your question re relative amounts of feathers in Norwegian versus Spanish Blue Tits might need to be refined by asking if the northern BlueTits have a greater percentage of down re total feather weight. That would require separating out all the down hairs and down feathers from the outer feathers – a near impossible task? A quicker way might be to measure the insulating qualities of various museum skins. I imagine they’ll all have roughly the same number of (countable) feathers but I bet that your Norwegian skins will have much more down hair and are thereby will be significantly cosier than your southern European ones.
Yes Murray, counting the individual feathers would be a somewhat thankless task! Measuring the insulating performance of museum skins definitely seems a more practical way of investigating the question.