Great Tits Have Culture And Immigrants Change It For The Better

Birds caught in the wild around Konstanz have been tested using puzzle boxes that give food when the puzzle is solved. Image Credit Sonja Wild

Scientists have observed the culture of a bird community changing when new members less tied to tradition are introduced, leading to a population better suited to the environment humans have made. Their work demonstrates the value immigrants bring to established communities.

Zoologists refer to culture in their subjects as behavior that is learned either from parents or peers, is widespread within a group, and persistent over time. Many mammals and birds have been shown to have it, including important cultural differences within a species, such as the “sponging” unique to dolphins of Shark Bay or the nut-cracking of some chimpanzees.

One of the best-documented examples of culture occurred among great tits (Parus major) after the introduction of foil-topped milk bottles. In 1921, tits in Swaythling, Hampshire were observed tapping holes in the foil to consume the cream. Other tits initially missed out on this abundant new food source, but gradually the practice spread, covering all of Britain within 20 years.

It was long suspected that some tits learned from others, with the innovation starting with one avian Einstein who taught others – although studies of North American birds threw this into question. It was only six years ago that scientists proved great tits can indeed teach each other techniques that become fixed in the population, at least as long as it's useful.

Max Plank Institute of Animal Behavior PhD student Michael Chimento wanted to know how persistent bird culture is when better options are available.

Chimento caught great tits in the forests around Konstanz, Germany, and placed them in 18 groups of six birds each. Every group had access to a puzzle box that provided food when solved. Each puzzle had two solutions, one more quick and efficient than the other.

In each group, one bird was taught the slow puzzle solution, which it then taught all the others. Once the inferior method was well established, Chimento replaced two birds in 9 of the groups with freshly captured tits that had never seen the puzzle before. New birds were substituted in again each week for the next three weeks.

In Current Biology Chimento and co-authors report groups with what they call “naive immigrants” were much more likely to adopt the more efficient route to accessing the food. Thus, the whole group benefited from the entry of outsiders.

"Experimental evidence of cultural change in animals is pretty rare, so we were surprised and excited by the outcome," Chimento said in a statement

Curiously, this wasn't because immigrant-containing groups were more likely to come up with a better method. In fact, the birds that had learned the old way were actually more likely to discover the better method than new arrivals.

However, where there were no outsiders present, birds would hit upon the better method, but seldom made much use of it, instead persisting with the inferior option they had been taught. On the other hand, the immigrants not only adopted the better method more quickly, but they also spread it to the original members of the group in which they were placed.

"Great tits seem to do well in and among human-made habitats, compared to other species," Chimento said. "Our study shows how their fluid social dynamics might be part of their secret to success and contribute to their flexibility."

For some species, substituting in new group members would be a very artificial and disruptive intervention. However, great tit social groups change with the seasons. They form flocks of around six in winter and break into pairs come spring, which may explain how the foil drinking innovation dispersed so effectively.

Sometimes puzzle solving gets tricky. Image Credit: Michael Chimento
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