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note a correlation between porphyrin in eggshells <strong>and</strong> nesting behavior. Pure white eggs are only found in <strong>birds</strong> which nest in shelter, such as under dense foliage, <strong>and</strong> which constantly attend <strong>to</strong> their eggs. Species which leave their eggs partly exposed <strong>to</strong> the elements have colorful porphyrincontaining shells, partially for reasons of camouflage, but also possibly due <strong>to</strong> the supposed temperature-regulating effect of porphyrins. Theoretically, it may be possible <strong>to</strong> detect porphyrin via chemical analysis of fossil <strong>birds</strong>. However, when res<strong>to</strong>ring <strong>birds</strong> with no preserved feathers, there should not be much for artists <strong>to</strong> consider that is not already covered by a working knowledge of melanin coloration. Porphyrins in feathers produce mainly only brown <strong>and</strong> dull red, colors that could also be produced with melanin alone. If anything, porphyrins give artists license <strong>to</strong> add extra reddish splashes <strong>to</strong> purely carnivorous species, especially those that may have been active at night or in cold climates. There are a variety of minor <strong>and</strong> less common pigments that can color a bird’s feathers. Pterins are responsible for the yellow, red, white, <strong>and</strong> orange colors of some bird eyes (in humans, eye color is controlled by melanin; low melanin results in blue eyes, <strong>and</strong> some babies’ eyes darken as their melanin levels increase). Flavin pigments cause many egg yolks <strong>to</strong> be yellow. Psittacofulvins are found only in some parrots, <strong>and</strong> create yellows, oranges, <strong>and</strong> reds in place of carotenoids, which parrots have evolved <strong>to</strong> sequester, possibly for nutritional reasons. There are (currently undescribed) pigments known only in penguins that add fluorescence <strong>to</strong> their yellow display feathers. In conclusion, Mesozoic <strong>birds</strong> would have taken their coloration predominantly from melanin <strong>and</strong> iridescent structural coloration. This would have resulted in a bird fauna possibly more drab overall than the one we see around us <strong>to</strong>day, due <strong>to</strong> the comparative lack of neoavians <strong>and</strong> their ability <strong>to</strong> color their feathers with carotenoids. However, like modern ducks, these <strong>birds</strong> would still have been able <strong>to</strong> create intricate <strong>and</strong> dazzling displays of color <strong>and</strong> pattern using combinations of earth-<strong>to</strong>ned melanins (muted yellow, rusty red, dark grey <strong>and</strong> off-white) as well as layering of iridescence <strong>to</strong> create striking, jewel-like feathers in blue, green, purple, <strong>and</strong> glossy black <strong>and</strong> white. While they wouldn’t have the pinks of flamingos or bright greens <strong>and</strong> yellows of <strong>birds</strong>-of-paradise, Mesozoic <strong>birds</strong> may have been just as beautiful. Opposite: Illustration of Jeholornis prima. 49