Conflict is universal throughout the animal kingdom, and flamingos, although they are known for their pink colors and ornate courtship dances, are no exception. When the birds feed, they also sometimes fight—and new research shows that flamingos with brighter colors tend to be more aggressive.
The study follows on previous research showing that birds with pinker plumage tend to be healthier, and to have a better chance of successfully attracting a mate.
Lesser flamingos (Phoeniconaias minor), the smallest of the six flamingos, are naturally found in sub-Saharan Africa, often along the shores of alkaline lakes, where they may form huge flocks numbering in the hundreds of thousands to more than a million birds.
With so many companions, it’s perhaps not surprising that lesser flamingo society is “complex,” says Paul Rose, a behavioral ecologist at the University of Exeter, in the United Kingdom. “Color plays an important role” in their social relationships, he says.
For instance, both male and female birds prefer mates that are brightly colored. But only birds that spend most of their time feeding and ingesting the right diet—one containing plenty of carotenoids, pigments that produce reds and oranges— will attain the most attractive hue.
“It’s an honest signal,” says Rose. “That pink color tells other birds that it’s healthy and fit.”
But these animals are also more aggressive, according to a paper published June 8 in the journal Ethology that observed captive flamingos in England. The finding could help researchers better raise the animals in captivity, experts say.
Although conservation organizations do not currently consider lesser flamingos as endangered, the birds’ numbers are declining in the wild; the International Union for Conservation of Nature considers them near threatened. Finding better ways to manage zoo populations will be important should the birds continue to dwindle. (Related: Meet Flamingo Bob, a poster bird for conservation.)
In their native habitats, lesser flamingos filter feed for aquatic organisms—crustaceans, algae, diatoms, and cyanobacteria—that contain the carotenoids that enable them to produce their color. In captivity, the birds are fed a special diet of pellets that provide the same pigments.
To examine the relationship between feather color and feeding aggression, Rose and colleagues made 210 one-minute videos of 45 of the birds (24 males and 21 females) in the various feeding situations at the WWT Slimbridge Wetland Centre, a wildlife sanctuary in Gloucestershire, England. He ranked the birds on a color scale with one being the palest and four the brightest pink. He then scored their foraging behaviors, taking special note of any aggressive actions. Most aggressive behaviors occurred when the flamingos fed inside in close quarters.
A flamingo might swiftly jab its head at a neighbor without actually making contact, which Rose says serves as a warning. If matters escalate, an aggressive bird might poke or peck violently at a companion, and even grab the other’s feathers with its beak while screeching.
A submissive bird might try to retreat from such a conflict, moving away with its feathers pressed against its body. But the winner often initiates a chase and attempts to grab the fleeing bird by its tail.
“It can be difficult to watch,” Rose says.
The price of being pink
The researchers found that flamingos with pinker hues were much more likely to initiate aggressive encounters and to fight.
“A healthy flamingo—which is demonstrated by its colorful feathers—is an efficient feeder,” Rose says. Such birds dominated the feeding areas Rose studied, and were especially aggressive toward others when fed from a bowl. By dominating the feeding situations, these bright birds ensured they would retain their rosy hues—which, in turn, helps them attract equally healthy and pink mates.
But such conflicts, whether in the wild or in captivity, have their costs, too. They disrupt the birds’ foraging, and may even lead them to disperse to new feeding areas—a change that can be especially harmful to captive flamingos, since aggressive displays can affect all the birds in a flock and reduce their feeding time. (Learn more: Like humans, flamingos make friends for life.)
“The link between plumage coloration and aggression is interesting,” says Melissah Rowe, an evolutionary ecologist at the Netherlands Institute of Ecology in Wageningen, “especially given the relatively few studies” into the effect of carotenoids on behavior.
Researchers studying carotenoids usually investigate how these pigments affect courtship and mate choice, adds Tom Pike, a behavioral ecologist at the University of Lincoln, in the U.K.
In a variety of species, from birds to fish, animals with brighter carotenoid-based colors have superior foraging abilities; they recover more quickly from diseases, and overall have better body conditions. Experiments with house finches have also shown that males with the reddest breast feathers are faster at taking flight and escaping from predators. Further, male sex hormones such as testosterone have been shown to work with carotenoids in male zebra finches, increasing the red hue of their beaks and making the birds more aggressive.
Whether similar changes occur in male flamingos eating a diet rich in carotenoids is as yet unknown.
At this point, researchers have only established a correlation between a pink hue and aggressive behaviors, but not causation. “Are pinker flamingos more aggressive, or are more aggressive flamingos pinker? It’s a subtle difference semantically, but there is a massive difference biologically,” Rowe says.
The study is “most important” for what it tells us about the best way to care for captive flamingos, says Rowe, suggesting that the results offer convincing evidence that the birds need sufficient space in captivity to avoid squabbling. “It’s good to see that this kind of research can improve the welfare of animals in zoos,” she says.
Rose says that his study has already led to positive changes at Slimbridge, where the caretakers built the flamingos a new indoor pool to help reduce conflicts.
Now the birds can spread out during feeding time, instead of being forced into food fights at a trough. “Flamingos don’t have any social skills, other than fighting, to resolve disputes,” Rose says. Giving all the birds better opportunities to feed will also likely make for a rosier-hued flock, which visitors love, he says.
“Zoos only need to make some small changes,” he notes, primarily giving the birds additional space when feeding. “There’s less waste this way and the flamingos are pinker,” he says—and, no doubt, happier.