A (nearly) serious crow question

[zharca]

Not sure I should stick my neck out and post this as I’ve managed to survive a few weeks here without managing to make myself look a total plonker. But here goes:

Here are a couple of thing that I read a long time ago, and I’ve been wondering about it ever since:

1 Many birds, especially the corvids, can see well into the ultra-violet. This is why UV bird scarers on airfields work, though we can’t see the beams.

2 "Black" things look black to us because they absorb all the spectrum that we can see.

3 (This is the bit I like) Corvid feathers quite strongly reflect ultra-violet (again shown by the fact that crows flying though the UV bird scarers can mess up the beams) I think we get a hint of this with the “oily black’ look of the crows and those iridescent magpie feathers.


Sooooooo – does that mean that on a nice sunny day a crow, to another crow, is actually a really brightly coloured bird?

To one another, do they look like tropical parrots, but with colours we don’t even have names for?

[goosey]

Gosh zharca thats a bit deep for me, but I actually get what you mean. Our cat is totally black but in the sunshine looks so brown she's almost red. I still can't answer you question though .

[leon-b]

i think things that are black dont absorb all the spectrum infact its completely the opposite, black is not really a colour its the absence of colour
i think lol
leon

[eeyore]

Originally Posted by leon-b

i think things that are black dont absorb all the spectrum infact its completely the opposite, black is not really a colour its the absence of colour
i think lol
leon

what you are saying is esentially the same as saying that black absorbs the whole spectrum - the colours we see depends on the frequencies of the light reflected to our eyes from the object - a black object absorbs virtually the whole spectrum and thus we dont get much light reflected from it causing it to appear black

so the second half of your post is correct but far from contradicting zhars statement you are actually agreeing with it

[Lords and Ladies]

Originally Posted by zharca

3 (This is the bit I like) Corvid feathers quite strongly reflect ultra-violet

and yet you never see them in nightclubs.. I think you're right, they are up to something.

[eeyore]

Originally Posted by Lords and Ladies

and yet you never see them in nightclubs.. I think you're right, they are up to something.

They dont go to clubs cos they are too busy raven

[Lords and Ladies]

ha ha ha

Brilliant.

[eeyore]

also they have trouble getting past the (jack)daw men... on the occasions that they do succeed they are really choughed

[Blackdog]

Originally Posted by eeyore

also they have trouble getting past the (jack)daw men... on the occasions that they do succeed they are really choughed

I don't know what you put in your tea Pete, but can I have some?

[Wild-Woman]

Originally Posted by Blackdog

I don't know what you put in your tea Pete, but can I have some?

Carrion like that Pete and we'll have to confiscate your keyboard.

[zharca]

seriously, though, i did a bit of digging and quite learned people have been researching this stuff:
------------------------------------
"Knowing that birds can see UV light, Bell Museum ornithologists Muir Eaton and Scott Lanyon (Director of the Bell Museum and Eaton's advisor) are looking to see how much various bird feathers reflect UV. Maybe there are important color patterns in bird plumage that the birds can see but we cannot. For all the time people have spent looking at birds, we've been unaware that birds see a much more colorful world than we do. Compared to birds, all humans are partially color blind. Eaton and Lanyon have found that there certainly are areas on many birds which reflect UV. It remains to be seen what the birds make of this, but it's a good guess that it's significant to them.
So seeing may be believing, it may also be humbling to realize that the world may not be as we imagine it should, but we have to learn to look carefully if we are to understand other animals because they, with their different eyes, may be seeing things quite differently from us."
------------------------------------

so doing a Google on "eaton lanyon ultraviolet" comes up with lots of very serious scientific papers like "The ubiquity of avian ultraviolet plumage reflectance" which, once you plough through them, say:

yes, crows are sorta bright er...er.."glod" colour.

which might explain the way the arrogant little sods strut around so.

[Lords and Ladies]

It's an interesting topic zharca.

I guess if these birds have evolved to see in ultra violet it must be useful for something.

I'm very confused over what reflects UV though. The flowers that attract insects with UV tend to be brightly coloured and show up on the UV films they sometimes show as a "bees-eye view". You don't get many oily black flowers.

I wonder whether they sell UV camera film so you could try taking some pics of crows and see what they look like.

[Wild-Woman]

As I understand it, blue tit males give off ultra-violet light which helps the females to identify them.

It's an interesting subject worth understanding more about I think.

[nightshade]

Drat WW I was going to say that

[almostnormal]

there are, as zharca has previously mentioned, some seriously hefty bits of reaserch about this. it takes some wading through, but its worth the effort if you're interested. i'm not sure about the UV films, i know you can get UV camera's, because dentisits use them to check out your tooth enamal!

[Wild-Woman]

Originally Posted by nightshade

Drat WW I was going to say that

Well you know the old saying about the quick and the disappointed.

Perhaps you give off UV rays that the Lioness finds irresistible.

[zharca]

Hi, I think the thing I find hard to visualise is that, to them, there are just *more* colours.

So, to us, something looks "blue" because it's absorbing the red and green light and only reflecting the blue. If it looks white to us, then it's reflecting all of the spectrum that we can see. Black absorbs all the ones we can see, but not necessarily all the ones they can, so it can still be a bright colour to them

What we call Ultraviolet is just an extension of the light spectrum so I think they will see several "extra" colours we just can't conceive of. The birdy-eye view of the world must be amazing!

So, to hijack another thread, maybe birds can tell a Marsh from a Willow Tit because one has a big stripe of UV colour right down its front?

[almostnormal]

nature is an astonishing thing i think.

perhaps that is how they tell themselves apart. oh if only we could see UV!

[nightshade]

Originally Posted by Wild-Woman

Well you know the old saying about the quick and the disappointed.

Perhaps you give off UV rays that the Lioness finds irresistible.

WW,I am a simple phernome man (coupled with good looks and a GSOH) I
do not as far as I know glow

[Lords and Ladies]

It seems you can try UV photography with fairly normal film or digital cameras so long as you use a UV filter to block the visible spectrum.

UV Colour Photography
UV tips
UV nature photography - some nice pics

[svenrufus]

Originally Posted by nightshade

I am a simple phernome man (coupled with good looks and a GSOH)

... sort of an Enchanters Nightshade then...?

[nightshade]

Exactly

[eeyore]

Originally Posted by Lords and Ladies

It seems you can try UV photography with fairly normal film or digital cameras so long as you use a UV filter to block the visible spectrum.

UV Colour Photography
UV tips
UV nature photography - some nice pics

just to point out that if you ask for a UV filter in jessops you will wind up with a clear filter which blocks the UV - for this application you need a more expensive filter which looks opaque as it blocks the whole visible spectrum and only allows UV to pass through.

[zharca]

Oh dear, the more I think about this, the more complicated it gets.
Here’s one for the photographers. I was thinking about how the bird colour world would work. We see colour light based on the colour wheel like this:



To make a bird version work it would have to be in three dimensions and would look like four billiard balls all touching, so each colour could still mix with all the others.

With our 3-colour model we can see these colours in additive mixing:
3 Primaries: R (red) G (green) B (blue)
3 Secondaries: R+G (yellow) R+B (magenta) G+B (cyan)
1 Tertiary: R+G+B (white)


Birds with their 4-colour one should be able to see these:

4 Primaries: R, G, B, U (ultraviolet)
6 Secondaries: R+G, R+B, G+B, R+U, G+U, B+U,
3 Tertiaries: R+G+B, R+G+U, G+B+U
1 Quaternary: R+G+B+U (this would be their white)

I make that six more colours we don’t even have names for

Next time someone asks “what colour’s that bird?”……….
I’m going for a lie down now……