Background
Smart birds are sexy
Female budgies prefer males that can solve problems.
Thursday 24 January 2019
Yeah, he’s cute. But does he understand that you cannot open a box if you’re sitting on the lid?

They say your brain is your biggest sexual organ, but it’s so well hidden you can’t really flaunt it at the beach. You need to do cool things with it to show what you can do. In fact, biologists suspect that this is one of the reasons that we have big brains in the first place. Being intelligent is practical for survival, but it’s sexy too. In biological terms: cognitive abilities are not just an advantage when it comes to natural selection, they give you the edge in sexual selection as well.

The difficulty with intelligence is that it’s hard to pin down. Everyone knows clever people and stupid people, but what makes someone smart? Are our IQs “what we measure in an IQ test” or do they actually tell us something, and if so, what? Of course, with humans, you still have the advantage of knowing what it’s like to be human. It’s rather more complicated with animals.

Nonetheless, over the last decade, there’s been much more interest in animals and their mental processes. “And following from that, we’d like to know how those processes were formed”, says Carel ten Cate, Professor of Behavioural Biology. In he scientific journal Science, the professor describes an experiment involving birds, that may help explain how those processes evolved.

Budgies

The experiment, designed by Ten Cate and one of his former PhD students, Jiani Chen, and carried out by Chen and two other Chinese biologists, uses male and female budgerigars. “These birds live in large groups, so they’re used to keeping an eye on each other”, Ten Cate continues. “They can live to a relatively great age for creatures of that size: twelve years or so. That means that the circumstances in which they live can change considerably, so it’s useful for them if they can rely on skills they’ve picked up. We know, from previous studies, that they can learn to do things they’ve seen other birds do. We wanted to know: does that make them more attractive to other birds? And how do we find out?”

The experiment’s setup is actually quite straightforward. Three cages are lined up next to each other: there’s a male budgie in the left one, a male budgie in the right one and the larger cage in the middle contains a female. The female can choose which of the two males she prefers to be near; that’s the male budgie she apparently likes best.

Next, the other male is given extra tuition. He is trained, step by step during sessions where he can’t be seen by the female or his rival, how to open boxes of food. Once he understands the tricks, he’s returned to his cage next to the female. The female is now exposed to two sights: the male she liked best trying in vain to open a box, and her initial second choice succeeding in that task. To make sure that she has a good look at the bird that is trying to open the box, a partition is placed between her and the male without a box.

Sellotape

The biologists sabotaged the untrained male’s box with a bit of Sellotape to prevent the him opening it by cleverness or sheer luck. “We weren’t testing the birds’ cleverness”, Ten Cate explains. “We wanted to create a contrast between an apparently smart bird and an apparently stupid one. That’s what the female bird gets to see, and what she responds to.”

The biologists were, of course, hoping that this new observation – hey, this bloke can do something the other one can’t! – will make the female change her preference. And that’s what happened. The ability to solve problems apparently makes budgies more sexually attractive.

Sexually? Yes, because if a female is put in a cage between two other female budgies, of which one has learnt a trick and the other hasn’t, she won’t change her preference.

Seeds

OK, but is it really about problem solving, and not because that male has food so he can take care of her? No, because if the bird that was rejected initially is given a lidless tub of seeds, one that does not require any solutions, she’s not impressed.

It would seem that sexual selection, in budgies at least, influences the evolution of intelligence. The females choose smart males and go on to have clever chicks who choose smart males and – wait a minute… The easiest box used in the test is a dish with a lid, which the birds often couldn’t open because they were sitting on it. The cognitive skill here – which was a real challenge for the untrained bird – consists of being aware that you cannot lift a lid if you are sitting on it. It’s not exactly rocket science.

So, for birds, the standards are not very high. Come to think of it, human problem-solving abilities are often quite disappointing too. If intelligence is so sexy, why is it so rare?

“There’s a price to pay for cleverness”, Ten Cate explains. “It has to do with intelligence being related to brain size. Brain cells use up a lot of energy, and making them requires a huge investment too. We assume that there’s a limit to the optimal extent of cognitive development. For each species, there’s a trade-off between intelligence and other traits.”

Bart Braun