Greater flamingos apparently aren’t fans of a sun-faded look for their neck feathers.
Scientists have known that the leggy birds touch up their color by smearing their necks with a serum they produce glands near their tails. But greater flamingos (Phoenicopterus roseus) aren’t simply enhancing color that’s already there; they’re also fighting the sun’s bleaching effect on it, researchers report in the October Ecology and Evolution. Feathers with a thicker coating of this serum held their color better than those with less, analysis shows.
Flamingos’ feathers help the birds fly, keep their bodies dry and attract mates. The feathers get their red color from carotenoids, molecules responsible for many natural pigments, found in the birds’ steady diet of brine shrimp and algae.
When flamingos preen, they care for their feathers a bit like how we care for our hair, cleaning out accumulated dirt and parasites. And like some of us, they add color. To apply their DIY feather dye, flamingos rub their cheeks on a gland above their tail called the uropygial gland, which generates a color-carrying serum. The birds then rub their serum-coated cheeks on their feathers and sway their necks to make sure the dye sticks. All that effort, paired with some slick dance moves, is aimed at attracting potential mates.
But the sun’s ultraviolet radiation can break down carotenoids. That got Maria Cecilia Chiale, a biologist at Universidad Nacional de La Plata in Argentina, wondering if flamingos lose their color without constant reapplication of the serum. If so, that might help explain their instinct to constantly “touch up” their plumage.
Chiale and her collaborators collected dozens of neck feathers from flamingos in France that had died in a cold snap (SN: 10/16/14). The team scanned the feathers and used Adobe Photoshop to analyze their color, and then placed half of them on a roof, exposed to sunlight. The other half were kept in darkness. Forty days later, new scans to analyze the feathers’ color intensity showed that the exposed feathers were sun-faded and paler than those kept in the dark.
Before the exposure experiment, Chiale had extracted carotenoids from both the surface and interior of each feather. After exposure, she found that feathers with a greater concentration of carotenoids had kept more color. That suggests that the birds had applied more serum to those feathers, letting them withstand fading better than those with a thinner coating.
Flamingos actively work to maintain their blushed necks throughout their lengthy display season as they prepare to mate, the research suggests; otherwise, they’d have pale feathers.
“Preening behaviors … have great social importance for flamingos because they live in large flocks and have synchronized behavior,” says Henrique Delfino, an ecologist at Universidade Federal do Rio Grande do Sul in Brazil who was not involved in the study. “Initially, the behavior was for [waterproofing], but since it reinforces the color signal of the feathers … it helps in the social communication of flamingos.” Without flashy feathers to advertise their health, flamingos probably struggle to find a partner.
All that preening to prevent feather fade doesn’t continue forever, though. Once they’ve snagged a mate and successfully hatched a chick, Chiale says, flamingos put the dye away, at least until the next year’s mating season. The concentration of carotenoids in the serum drops dramatically, and the flamingos apply it far less frequently.
“They don’t need to have makeup on while they’re raising the kids,” she says. They need that energy to take care of their chicks.
sciencenews.org, 26 October 2021