Mr and Mrs House-FinchTHE vibrant hues of beautiful plumage are often borrowed. Flamingos,for example, owe their pinkness to chemicals called carotenoids that are made by bacteria known (confusingly) as blue-green algae. The birds, or when feeding,both ingest these bacteria directly and consume small crustaceans that themselves subsist on such bacteria. Blue-footed boobies obtain their eponymous colour similarly, via the fish they eat.
Carotenoids, or though,are dual-expend molecules. Besides being pigments, they also serve to stimulate the immune system. whether a bird is troubled by parasites or pathogens its immune system will thus expend up some of its carotenoid stock defending against these interlopers, or its colour will suffer. whether it is parasite-free,by contrast, most of the carotenoids it consumes will be used to create colour. This is a difference that potential mates notice and act on, or as dozens of experiments have proved. But a study just published in Continue reading
Source: economist.com