Bird’s-Eye View
I was excited to see the current New Scientist special on bird senses. This is a photo of a red-tailed hawk that I took. Now consider: “Raptors can see to distances far greater than we can. One reason for this is that the light-sensitive layer at the back of our eyes, the retina, has one fovea, a sensitive spot where the image is sharpest. Raptors, in contrast, have two foveae in each eye, which is equivalent to a camera having both a telephoto and a macro lens.”
And to think I was taking a macro shot with my digital prosthesis… Oh, but it gets much stranger. Humans and birds have left and right hemispheres in their brains…but…
“We now know that birds’ brains are more lateralised than our own. Intriguingly, in birds with eyes located on the sides of their head, this extends to using the left and right eyes for different tasks. In day-old chickens, for example, the right eye tends to be used for finding food while the left scans for predators. You might imagine this difference to be hard-wired – genetic – but it isn’t. Just before a chick hatches, it has its right eye facing outwards, which means it receives some light through the shell. The left, inward-facing eye gets no light. However, if you gently turn the chick’s head in the shell so that the left eye gets most light, lateralisation is reversed.”
From http://www.newscientist.com/article/mg21929282.600-bird-senses-vision.html#.UggjGBaU1zo
Birds also see a wider color spectrum than we do. Humans have three types of cones (RGB color space), and birds have at least four dimensions of color vision, taking them into the ultraviolet end of the spectrum.
Increased dimensionality produces a qualitatively different color perception, one that we cannot intuitively understand.
“The tetra- or pentachromatic color space of birds appears to be the most complex in nature and is likely involved in virtually all areas of the animals’ lives, from the discrimination and recognition of objects to more complex behavioral tasks such as navigation, the classification of objects, and social and sexual behavior.” More info: http://birdsandlighting.com/articles/cvb.html
And if you are still not impressed consider their sixth sense for long distance navigation across the planet…
“We still do not know exactly how it works, but what we do know is mind-bogglingly bizarre.
First, birds seem to detect the direction of the magnetic field using microscopic crystals of magnetite – a magnetic form of iron oxide – located around their eyes and in the nasal cavity of the upper beak. More recently, it has emerged that they may also detect the strength of the field via a chemical reaction – physicists have known since the 1970s that certain chemical reactions can be modified by magnetic fields. Stranger yet, studies of the European robin indicate that the reaction involved is induced by light entering the bird’s right eye only. Researchers are currently striving to find out where in the body the reaction takes place. Meanwhile, some speculate that it might allow birds to “see” the contours of the Earth’s magnetic field – something that is difficult to envisage as a mere human.”
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