It appears that birds of a feather really do flock together.

A new paper published in Behavioural Processes suggests that flamingos develop long-term friendships, technically called associations, with other birds in their flocks. 

Paul Rose, an ornithologist at the University of Exeter and the lead author on the paper, photographed four flocks of flamingos at the WWT Slimbridge Wetland Centre several times a day for three years. He used leg tags to differentiate individual birds. Within each flock, he found groups of two or three birds that were consistently standing close, or within one flamingo neck-length of each other.

The friendships formed across ages and genders. Rose saw two female flamingos born in the 1960s who were routinely joined by a male flamingo twenty years their junior. He didn’t see any flamingos that appeared to be social outcasts. Some birds stayed close to their associates while others were more likely to mingle in different groups.

Rose said flamingos might look like they are just standing in a big pink mass, but within that group individuals are making choices about where to stand based on their associations. 

Unlike other social animals like monkeys that groom each other, there was no obvious activity that the flamingos were sharing.

Rose said he has “wracked” his brains trying to figure out why the birds are forming the relationships. His personal theory is that flamingos stick close to birds they like to avoid fighting with other flock members. Rose said flamingos have to live in big, gregarious flocks because all the birds share limited territory and resources.

“You might as well know who you get along with so you don’t waste energy squabbling,” he said.

Rose said zoos should aim to house large flocks of flamingos. This allows the flamingos to have more choices for their BFFs – or bird friends forever.

Chris Tuite, an ornithologist who works with the Maasai Wilderness Conservation Trust, said the data from Rose’s study fits with his anecdotal observations of the lesser flamingo in Africa. Since lesser flamingos live in large flocks and all look the same, Tuite said it is impossible to identify individuals.

“However, from observing them in many different situations, it seemed that often when one or two left a flock or area, several others would join them but not a whole larger group,” he wrote in an email. “So it was possible to imagine that there were groups that stayed together within larger flocks.”

He said it makes sense that flamingos would maintain associations to learn information about migratory routes or the locations of suitable lakes.

Kevin McGowan, a scientist at the Cornell Lab of Ornithology, said there hasn’t been much evidence of long-term bird associations because it is difficult to observe individuals in large flocks of birds. 

That’s why Rose chose to observe captive flamingos that were tagged and could not fly away to new lakes.

McGowan said he has looked for similar patterns in American crows with tags on them. He did not find any patterns of non-familial attachments. Crows have long-term relationships with their mates, and McGowan has observed adult siblings hanging out together.

Rose’s study did not look at mating behavior or whether friendly flamingos were siblings or cousins. Rose said studying if mating plays into the associations could be an area of future research.

McGowan said Rose’s findings make sense. He said it would be weird if flamingos in a flock didn’t recognize any of their flock-mates. Birds might not be people, but they also aren’t particles floating around at random, McGowan said.

“Even though it just looks like a big flock of pink flamingos, they are individuals and they know each other to some extent,” he said.

McGowan said there have been a lot of studies done in captivity with interesting results, but they don’t always translate in the wild. Chickens, for instance, have pecking orders that aren’t observed in wild birds. He said it is possible that being stuck in a flock in captivity could alter the flamingos’ social behavior.