Читать книгу Bird Senses - Graham R. Martin - Страница 51

Just how the world might look when viewed through the birds’ tetrachromatic colour vision system is of considerable interest. For example, does tetrachromatic vision mean that particular parts of the spectrum have different salience to birds compared with our own view of the world? Certainly, knowledge of the tetrachromatic system suggests that birds’-eye views are likely to be different to how humans detect colour information in the world. Of course, it is not possible to see these colours through birds’ eyes, but computational methods have sought to compare colour patterns viewed through trichromatic and tetrachromatic vision systems, and have given some clues as to which kinds of differences between natural colour patterns are changed by a tetrachromatic system.

All of these differences in spectral sensitivity and colour vision, however, apply only at high (daytime) light levels when the cones are active. At lower (twilight and night-time) light levels, only the rods function and they have very similar characteristics across all birds and across mammals. Thus, at low light levels a similar sensitivity across the spectrum, and an absence of colour vision, is found in all bird species and indeed in humans and other mammals.