We always assume the world is just the way we perceive it. Especially when it comes to colours and depth, movements and textures. But also consider sound, for example. Is there really no sound, when we hear silence, or is it just that we can’t register it? In the series Nature meets Philosophy, I will find more about what we cannot perceive. First up: can birds see more colours than we do?
On the risk of sounding terribly vague and philosophical, I have to get this of my chest. From time to time, I wonder what sounds and things and who-knows-what there are that we humans just cannot perceive. After all, we are no super-organisms. We have our limitations too.
So what if there is so much more that we do not know about?The first time I really got conscious of this idea was during one of the lessons in Ancient Greek in high school. We had an awesome teacher who let us talk about philosophy for hours (as long as we made sure we finished our translations too). It was during one of these classes that we came up with the idea of “kraly”, a colour that we cannot see. Needless to say, that “discovery” kept us busy for quite some time.
The idea is not so strange, though. Our eyes are adapted to see only certain colours. Other colours, consisting of wavelengths outside of our spectrum, we simply don’t see. Probably because these colours have not been vital in the lives of our ancestors, way back when our eyes evolved. If we for example compare our sight to that of birds, there immediately is one striking difference. They can see ultraviolet light, while we obviously can’t. Because of that, many birds actually have patterns in ultraviolet on their feathers.
It even happens that some of the bird species where we can’t see the difference between male and female, well, they have different ultraviolet patterns for the different sexes. The Eurasian Blue Tit (Cyanistes caeruleus) is an example of that. You probably see them in your garden or neighbourhood very often, so it is kind of strange to realize they have these “exotic” colours, hidden from us.
Also for other purposes, seeing ultraviolet light comes in handy for a bird. While hunting, for example, a bird can see the ultraviolet light emitted by certain compounds in urine. If a small rodent leaves drops of urine every now and then while walking, it forms a perfect trail for a hunting kestrel to follow. And that makes finding food suddenly a whole lot easier for the bird. Quite smart, I think.
All together, it makes you consider how much of the colours in the world you are actually seeing. Now we have only talked about one colour, of which we already know the existence. What about all of the other possible colours we do not yet know of? I think it’s quite amazing.
Can you imagine there being colours we cannot see? Do you look at birds in a different way now?