Any zoo placard will tell you that flamingos get their vibrant pinks from eating algae and crustaceans like shrimp that are loaded with carotenes; it’s the same thing that gives carrots and pumpkins their color. Once ingested, these pigments circulate in the blood and accumulate in keratin, a key component of feathers. According to a new study, the first bird to display carotenoids in its feathers lived at least 56 million years ago, and birds have steadily become more colorful over time.
Brightly colored males are generally sexier to females than those with dull plumage. But when did that start to happen? Fossil feathers have shown that black and brown melanins have existed for at least 160 million years. But without any trace of carotenoid pigments in ancient feathers, a team led by Daniel Thomas from the Smithsonian Institution had to look for the evolutionary origins of bright colors and warm hues in the feathers of living birds.
First, they visually surveyed 9,993 species of modern birds and found that red, orange, yellow, pink, or purple carotenoid pigments are in the plumage of nearly half of our living bird families (that’s 2,956 species). Then the team chemically analyzed the distribution of plumage carotenoids to confirm their presence in 95 of the 236 existing families of birds. (Only 36 family-level occurrences had been confirmed previously.) Finally, the team plugged their data for all modern birds into a model to reconstruct the evolutionary history of plumage colors.
Their findings show that carotenoid-pigmented feathers appeared multiple times, and independently, in 13 orders of birds including ducks, storks, and cuckoos -- who are not particularly famous for their colors. Based on time calibrations from the family tree they constructed, the number of bird families displaying plumage carotenoids increased throughout the Cenozoic (going back 65 million years until now), and most of the plumage carotenoid originations occurred after the Miocene Epoch, 23 million years ago.
The earliest origin of plumage carotenoids, they found, was within the order Passeriformes. These are perching birds that include our everyday sparrows, robins, and crows -- but not flamingos, which belong to order Phoenicopteriformes. So instead of a flamingo, picture more of a cardinal. This theoretical perching ancestor lived during the Paleocene Epoch between 66 and 56 million years ago.
Their findings are especially surprising given how 100 percent of existing flamingo species accumulate carotenoids in their plumage -- yet only 41 percent of perching bird species and less than 1 percent of duck species (order Anseriformes) have carotenoid-consistent plumage colors.
The work was published in Proceedings of the Royal Society B this week.
Images: Brian Fagan (top) & BobMacInnes (bottom) via Flickr CC BY 2.0