Birds Are Blatant Conformists

Learned social behaviours, like whether rocking a J. Crew pullover is cooler than a leather jacket, spread through human social networks via a complex interplay of many factors, including observation and conformity. Birds aren't that much different.

Zoologists have known about imitation-based social learning in birds since the 1920s. A small population of birds in the small village of Swaythling, now a suburb of Southampton in Britain, was observed opening milk bottles with their beaks in 1921. Over the next 20 years, zoologists tracked the practice's spread across the whole of the UK.

Seven decades later, researchers at Oxford University have quantified the structure of great tit social networks and developed a method to engineer the spread of new behaviours. A study outlining their results was published today in Nature.

According to the paper, over 90 percent of the great tit population in the Wytham Woods, where the experiment was conducted, are tagged with RFID devices that track their location. The researchers also set up automated feeders throughout the woods that collected data about the birds that fed there at certain times. By combining the data from these two sources, the team was able to determine which birds were meeting up with each other more often, and where.

"What you typically find is that an individual has strong associations with a few individuals, and then weak associations with many more," Ben Sheldon, the study's lead author, told me. "They're not connected to that majority of the population at all, but they are connected to them via links to other birds."

In other words, bird social networks are pretty similar to humans', in principle at least. Like birds, our social networks are composed of strong and weak connections, determined by the amount of interaction we have between them.

Knowing this, the researchers decided to see if they could introduce a new behaviour into five different subpopulations of great tits in the Wytham Woods and observe how they spread throughout the networks formed by the birds in those areas.

The team first trained ten captive birds—two for each subpopulation—to open a box containing tasty mealworms by moving a sliding door either left or right. They then released the birds back into their original populations. They discovered that the wild tits formed strong biases as to which direction the door should be opened, depending on which trained birds were in their network. When they repeated the experiment one year later, these practices persisted.

"Despite the fact that they discovered both solutions, they showed increasingly strong bias for the majority behaviour at the time," Sheldon explained. "It's almost as if they're ignoring their personal information about the fact that they can open this both both ways, in favour of what the majority is doing. It's like a positive feedback effect."

According to Sheldon, these findings confirm that birds learn social behaviours through conformity on a large scale.

"We know that humans and primates do this, but certainly nobody had seen this in a wild bird population. It suggests that this might be a more common behaviour than we realize," he said.

Knowledge on the mechanics of how behaviours spread through large populations of birds could hold explanatory potential for previous findings. For example, researchers recently found that chaffinch songs lose their syntax as the populations stray further from the mainland, essentially becoming a chorus of free-wheeling chirps.

While we don't know exactly why this occurs with any certainty, Sheldon believes that bird social network theory explains how large differences between populations emerge in the first place.

"It's a mechanism that causes a population to develop a very, very strong bias in a particular direction. You get a positive feedback effect where one population moves increasingly towards an extreme," he told me. "We don't know if that applies to something like song learning, but, if a similar process was happening, that is something that would very rapidly produce differences between populations."

In the end, it appears as though birds are really just a bunch of conformists, imitating the behaviour of their pals. I wonder if they even have their own terrible memes—what's the great tit version of the Ice Bucket Challenge?