Great tits and bad food


Research finds birds modify their food choices through watching television. Andrew Masterson reports.


A great tit watching one of its peers have an unfortunate food experience on television.
A great tit watching one of its peers have an unfortunate food experience on television.
Liisa Hämäläinen

Birds can learn to avoid unpalatable food simply by watching other birds attempt to eat it on television.

The discovery – by a team led by Rose Thorogood, from the UK University of Cambridge's Department of Zoology – is not only startling in its own right, but also solves one of the lingering issues related to the role of warning colouration in predator-prey interactions.

It’s long been established that many types of prey species – including insects, amphibians and fish – signal their own toxicity through bright colouration. The colours, the theory runs, serve to warn potential predators that eating a particular animal will have unpleasant and counter-productive consequences.

The idea is sound, and well supported by evidence of toxicity in brightly coloured species, but it does beg a question. How does a predator learn about the warning signs without first eating the brightly coloured prey – an action that can lead to the death of both participants, thus rendering the lesson utterly pointless?

The new research by Thorogood and her colleagues provides an answer. In birds known as great tits (Parus major), at least, individuals learn by observing the unfortunate experiences of their peers and avoid repeating them.

To demonstrate this, the scientists used a number of wild-caught birds and kept them in aviaries that were decorated with bits of white paper dotted with small black crosses. Some of these bits of paper were wrapped around slices of almond, filling the function of camouflaged prey. The birds quickly learned to unwrap them and devour the food.

In the next phase, one tit was encouraged to unwrap a piece of paper decorated with a black square – a food source much more conspicuous than the cross-decorated ones. This little parcel contained almond dipped in foul-tasting bitter liquid. After trying it the unfortunate bird made its displeasure known, by shaking its head and wiping its beak.

Thorogood’s team filmed this unpleasant encounter and then replayed the footage to some, but not all, of the rest of the tits.

After seeing the material, the exposed birds were 32% less likely to try to eat the contents of a conspicuously marked food package than those which had not viewed the scene.

Thorogood calls this type of learning “social transmission”.

“Just as we might learn to avoid certain foods by seeing a facial expression of disgust, observing another individual headshake and wipe its beak encouraged the great tits to avoid that type of prey,” she says.

“By modelling the social spread of information from our experimental data, we worked out that predator avoidance of more vividly conspicuous species would become enough for them to survive, spread, and evolve.”

She adds that the experiment indicated social transmission was essential for warning colouration to have any survival benefit for animals at either end of the predator-prey equation.

“Without social transmission taking place in predator species such as great tits, it becomes extremely difficult for conspicuously coloured prey to outlast and outcompete alternative prey, even if they are distasteful or toxic,” she says.

“There is mounting evidence that learning by observing others occurs throughout the animal kingdom. Species ranging from fruit flies to trout can learn about food using social transmission.

“We suspect our findings apply over a wide range of predators and prey. Social information may have evolutionary consequences right across ecological communities.”

The research is published in the journal Nature Ecology & Evolution.


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Andrew Masterson is news editor of Cosmos.
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