The colours are all in your head man!

The colours of a Kestrel are 'behavioural' - they are designed to effect the eyes, therefore the brains, therefore the behaviour of other animals - of other species - camouflage, and the same species - communication.

Autumn is a time when, probably more than any other, we’re aware of colour in nature.  At the risk sounding like Philomena Cunk….but what is colour?  

The greenness of a leaf isn’t something inherent in a leaf - it’s a sense perception in the brain. Sunlight hits the leaf, chrolophyll absorbs certain wavelengths of light to produce sugars by  photosynthesis.  The wavelengths which aren’t  absorbed are reflected. This light hits our eyes when we look at a leaf, - the brain interprets this with a sensation of “green”.*

Colours are things our brain invents – they help us make sense of, and navigate through the world. Our  brains are therefore measuring lengths - the wavelengths reflected by different objects in the world - this give us useful information about the world.

Our fellow members of the animal kingdom have similarly wired brains (in that they can also perceive colour) which is why we have things like patterns on a moth – camouflage,  and a Robin’s breast - communication.

Colour in biology could be categorised in the following way:
1. Metabolic – chlorophyll is a good example.  The leaf ‘needs’ the property – which we perceive as green – in order to photosynthesise.  This is, in turn, determined by the physical properties of light.

2. By-products – colours that don’t serve a function - they occur 'willy-nilly'.  Autumn leaves are a good example.  Chlorophyll degrades into colourless compounds at the end of the growing season. This reveals the otherwise hidden pigments – the browns and yellows.

3. Behavioural – colours which are designed to effect the brains, and thus behaviour, of other animals.  These are animals of other species – as in camouflage, as well as members of the same species as in communication.

Dead leaves of  Silverweed (which incidentally look remarkably feather-like). the greens in the photo are 'metabolic' i.e due to light refecting properties of chlorophyll, the browns are by-products i.e don't serve a specfic function.

Alternatively you could look at it from an ecological point of view – an analogue of the food chain. 

1. Primary  - the colour of producers – green plants –  determined by the properties of  sunlight.

2. Secondary - the colour of some consumers – some insects for example (but not cows!), is green so that they reflect light of a similar wavelength to the leaf they’re sitting on.  Light from both the leaf and insect hits the eye of a predator.  This makes it more difficult for the predator’s brain to discern an outline – thus we have camouflage.

3. Tertiary - the colour of the prey species effects the evolution of the brain of the predator in a way that enhances its ability to discern an outline.

It's an interesting thought that, if there were no eyes in the world (human or otherwise), there would be no colours in the world.

Equally there would be no sounds without ears, as this applies to all senses not just vision. Sound, taste, touch are also things our  brains invent as a response to physical phenomena ’out  there’. They allow us to create a mental model of the world.

If you wanted to take a step back and include the non-biological world in an overview of colour, you could divide things like this:

1. Abiotic – colours independent of biological processes. This in turn is comprised of:
              a)      Colours dependent on the properties of sunlight – the blue of the sky for example
              b)      Colours independent of  sunlight (but probably not independent of the sun itself) – the ‘rock’ colour of rocks for example.
2. Biotic – colours which depend on biological processes – all those described above.

Philosophers have a lot of fun with the question  - when I perceive 'green' - do you perceive the same thing...and is it possible to ever know?  Do other species perceive the same thing?

What about our emotional responses to colours? One (contentious) theory is that we react favourably to green in the countryside, because our original habitat was African forests and therefore we feel ‘at home’...

..but that's a whole other kettle of cheesy wotsits (and indeed vat of quavers)  - I’m off to enjoy some autumn colours!

Bleeding Oak Crust (Stereum gausapatum) the amber colour of the exuding droplets is (probably) a by-product i.e. doesn't serve a specific function (I stress 'probably' as I don't think anyone knows)

The colours of the Bee Orchid flower are 'behavioural' - they have evolved to effect the brains and thus behaviour of bees which act as the orchid's pollinators

* please note these categories and terms are things I’ve come up with. I’d hate anyone to fail their homework after reading this!!

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  1. I didn't know half of that what and interesting post, thanks for sharing (and educating).

  2. An interesting and informative post on a subject I have to admit I given much thought to (at least not in an in-depth kind of way!) since university days (which were quite a long time ago!). Great images of the Kestrel and beautiful Bee orchid - a flower I'd love to see.

    1. Cheers Jan, Bee Orchids are reasonably easy-ish to see around here - on the coast - Ainsdale is a brilliant place for orchids and plants in general, but you get them at Marshside and Martin Mere as well - my patch gets well and truly Orchided as well - mostly Northern Marsh, but I was delighted to find some Bees here as well in July

    2. Thanks for the tips - I will look out for these pretty orchids if I'm over that way in the summer. I've never seen Bee orchids locally (I could have missed them of course!) but this year did seem to be a good one for what I think are Common (though might be Heath) Spotted orchids. (I put a photo on a blog on Swettenham in July if you know your orchids?)

    3. Hi just, just had a look at your July Orchid, as the 3 lobes of the middle petal are the same size, it looks like Common. re Bee Orchids - just had a look at my ancient copy of the Flora of Cheshire (pub. 1971)- it's listed as very rare with just one record. I don't understand that as there seem to be a lot more Bee Orchid localities in Cheshire

    4. Thanks for looking and confirming the ID. Thanks for the link too - with the map resolution at 10km squares it looks like Bee orchids must be everywhere in Cheshire, but at 2km res the records get quite sparse. That stretch of NW coast you mentioned looks much more promising! :)


    5. I can recommend a visit to the Ainsdale dune reserve in summer - a brilliant place for special plants, insects, Natterjacks, lizards. The beach is a stones throw away and can be teeming, but few venture into the dunes

  3. This is an fascinating read! A few points I had not thought of here to mull over. All makes good sense.


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