Although responsible for some intraspecific variation in colouration, colour changes cannot explain the extreme phenotypic diversity in colour patterns found in many species.
Furthermore, among the 19 species in the Paradoxornis genus there is apparently a pronounced variation in egg colouration with ground colours being described as white, green-white, grey, yellow, brown, reddish, pale blue and blue.
To this end, the intensity of red of the dorsal fin was measured relative to the amount of red exhibited in the body (variation in body colouration was more likely to reflect differences in diet and less likely to be a direct target of sexual selection; NB: although the body had very little red in its colouration generally, there was still variation in body colouration among populations – [ 28]).
Despite relatively small intra-individual variation, the changes in plasma carotenoid levels were still reflected in individual variation in tarsus colouration between the 2 years.
[14], [15] Tetrix japonica occurs in both grass and sand microhabitats and exhibits large variation in body colouration and markings.
For example, in cichlids LWS opsin expression varies with water turbidity and it appears that population-level variation in wavelength sensitivity has played a role in variation in male colouration [21].
There is some variation between the three subspecies, especially in the colouration of the underparts.
To this end we determined the relationship between colouration and detectability for great tits and blue tits, using data on the natural variation in colouration of adults and fledglings, in combination with experimental manipulation of carotenoid availability during moult.
A very interesting phenomenon associated with colour polymorphism is homochromy, which describes matching of body colouration with variation in the background pattern of the local habitat [ 14, 15, 20, 35].
In Lake Tanganyika, the endemic genus Tropheus represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved.
