麻豆淫院

Birds are some of the most striking creatures on Earth, coming in a rainbow of colors that serve several important functions, such as attracting a mate and communicating with other birds. These vibrant hues are produced by pigments, primarily melanin, but a major unknown until now was how much these pigments weigh. Since wings need to be as light as possible for flight, understanding pigmentation weight may tell us something about the trade-off between the evolutionary benefits of colored feathers and the physical cost of carrying that weight.

In a new study in the journal Biology Letters, scientists from Spain have investigated how much melanin adds to the weight of feathers and the difference in weight between the two main chemical forms of melanin鈥攅umelanin (responsible for brown and black colors) and pheomelanin (responsible for reds and lighter colors).

The researchers analyzed the feathers from 109 bird specimens across 19 different species, including the common kingfisher (Alcedo atthis), the golden eagle (Aquila chrysaetos) and the Eurasian bullfinch (Pyrrhula pyrrhula). They examined feathers with mixed colors and those with single, pure colors, and used a chemical process involving sodium hydroxide or caustic soda, as it is more commonly known, to extract the pigments. Once extracted, they were weighed and compared to the original weight of the feathers.

According to the scientists, melanin pigments account for about 22% of a feather's total weight, and in the most pigmented feathers, this weight is no more than 25%. Additionally, the two types of pigments don't weigh the same. Eumelanin, which makes feathers black or brown, was significantly heavier than pheomelanin, which produces lighter colors.

The paper suggests that a bird has to expend more energy to carry the weight of certain feather colors, which could explain why birds have evolved such a wide variety of hues, as the scientists write in their paper. "Our findings introduce a novel metabolic cost for flight associated with different plumage phenotypes that may help us understand the evolutionary predictors of bird color diversity."

Taking the findings a step further, the researchers suggested that birds in cold climates, like snowy owls, didn't just evolve white feathers for camouflage. The lack of a heavy pigment would allow them to grow thicker, more insulating feathers without adding too much weight. Therefore, they can stay warm and still be able to fly. Additionally, migratory birds may have evolved lighter feathers to reduce the energy cost of flying long distances.

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