Martin Nicolausson


For the past few weeks, my eight-year-old son Amit and I have spent many hours avidly observing birds, paying attention to their individual and particular behaviours. We noticed that some we studied were different in their physical characteristics such as colour, shape and size, and that these traits varied with behaviour. This made us wonder about the possible evolutionary links between the appearance of the birds on one hand, and their respective behaviour on the other.

The first difference that stood out to us was between the small and large red birds. Although the larger ones were about twice as big, their ability to fly was about the same. But what was very different about the two subtypes was that the larger variety were much more aggressive and caused more damage when they attacked. And although we often observed that the smaller red bird also attacked, it did so in a much gentler way. Of course, the evolutionary reason for this difference in aggression seems straightforward: the birds that evolved to become larger need more food; with this increased requirement, aggression becomes an important survival skill.

The link between the appearance and the behaviour of the yellow birds was slightly more of a challenge to figure out. Other than being yellow, their general characteristics were similar to the red birds', but Amit and I couldn't help notice their tendency to suddenly fly at much faster speeds relative to the red birds. We speculated that the evolutionary reason for this difference must be that the red birds, by virtue of their threatening colour, are less appealing to predators, so as a consequence they never needed to develop enhanced speed to escape. In contrast, the yellow birds with their appealing hue practically invite predators to dine. With this clear disadvantage the yellow birds are forced to rely on an alternative survival mechanism, in this case the valuable skill of increased speed.

Another interesting feature of the yellow bird is that it has a sharper shape, perhaps because it is a species connected to the woodpecker family. The sharpness might also help it when it needs to break down a structure or cut through wood.

The blue birds were fascinating in their ability to self-replicate, and in all of the cases we observed they produced exactly three offspring. We wondered why the blue birds evolved to produce offspring at such speed and consistency, and determined that it must be because the blue birds are small and slow. These disadvantages force this type of bird to develop a skill for reproduction, thereby hedging their bets and increasing the potential to pass on their genes despite their size and speed.

The white birds were even more puzzling. On multiple occasions, we watched them as they dropped their own eggs while in flight. Initially this seemed to be a counter-evolutionary strategy, but once we inspected the discarded eggs more carefully, we realised that they were abnormal, and this was probably the white bird's strategy for dealing with eggs that have a low potential for survival. One observation in support of this hypothesis is that the white birds seemed to be much healthier, lighter and happier after discarding eggs.

Amit and I are thinking that we would like to continue pursuing this project for the near future, spending even more time in this educational activity. In fact, we are getting somewhat addicted to it -- and we have just learned that there are plenty more birds to observe in Rio.

But what really baffles us is this: why are these birds SO angry?

Dan Ariely is the James B Duke professor of psychology and behavioural economics at Duke University, North Carolina, and the author of The Upside of Irrationality (HarperCollins). Amit is eight and likes animals (even angry ones), digital zoology, Lego and negotiating with adults


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