Uek has a problem. She can see a piece of food through a hole in a plastic box, but she cannot reach it. Fortunately, Uek is a New Caledonian crow, a bird that is both intelligent and adept with tools. She grabs a stick with her bill, pushes it forward through the hole and knocks the morsel onto a slope,. It rolls within her reach, and she tucks in.

Kermit has an even bigger problem. He’s faced with the same out-of-reach snack. He has the same stick and the same smarts. But Kermit is a kea, a green parrot with a sharp, curved beak. He can’t wield a stick with the same precision as Uek with her short, straight beak. So Kermit improvises. He picks the stick sideways in his beak and pushes one end through the hole. He holds it there with his foot, grabs the other end in his beak, and finally (and awkwardly) pushes it at the food. Eventually, he too gets a meal.

Uek and Kermit are members of arguably the most intelligent groups of birds – the parrots and the corvids (the family that includes crows, ravens, jays and magpies). For their size, their brains are roughly as big as those of great apes, and their behaviour can be just as sophisticated. They’ve shown many advanced skills including planning for the future, using tools and solving problems.

Now, Alice Auersperg from the University of Vienna has challenged them to the same task. The obvious question is: which one did better? Who is the brainiest of the bird brains? But that would miss the point.

Animal intelligence isn’t a single thing. There is no standard IQ test for them to sit, and no universal checklist of skills to score them against. Instead, animals have evolved mental abilities to cope with different lifestyles and environments. Many early studies into animal intelligence simply looked at whether animals could or couldn’t perform specific tasks. But it’s far more interesting to see why and how they do different things, and how their own particular brand of intelligence has evolved.

That’s why Auersperg, along with Alex Kacelnik from the University of Oxford, decided to work with two of the planet’s brainiest birds – not to pit them against each other, but to understand how they differ.

She presented five New Caledonian crows and six keas with the same set-up – a puzzle box with food, balanced on a central pole. If the birds could knock the food off the pole, it would roll down a sloped platform into their grasp. There were four ways of doing this: they could pull a string tied to the food; they could open a window and stick their head into the box; they could roll a marble down a chute to knock the food off; or, they could push the food off with a stick. Two of these solutions – the marble and the stick – involved tools, and the others didn’t.

The birds could approach the task in any way they liked. And every time they learned one of the four tricks, Auersperg closed it off, forcing them to find a different solution.

She found that at least one bird of each species – Uek and Kermit – discovered all four techniques, which shows that they’re certainly capable of doing so. But the similarities ended there.

Keas are notoriously inquisitive and attracted to new things. In its native New Zealand, it uses it beak to explore (and destroy) everything from nests to picnic baskets to windshield wipers. All of Auersperg’s keas immediately (and violently) explored all four openings in the box, pulling, tearing, scratching and probing at them. “They seemed to approach the apparatus in a playful, toddler-like manner,” she says. Most of them tried to overturn the box, which Auersperg had to nail to the floor. One of them, Luke, even broke the Plexiglas.

As a result of their gung-ho investigations, they picked up the four solutions to the puzzle far quicker than the crows did. After their first session, they had already discovered at least two or three, and when each one was blocked, they moved onto the next one with great speed.

In stark contrast to the keas, New Caledonian crows shirk from novelty. Rather than rushing in beaks first, they explored the box by sight before giving it some tentative pecks. One of them never even went near it. As such, it took them longer to pick up the different solutions.

But the crows had an edge – they’re natural tool users. In the wild, they manufacture their own tools to “fish” for insect grubs buried within decaying logs. In captivity, they’ve chosen the right tool for different jobs, combined different tools together, and improvised from unusual materials like wire hangers. Keas, however, aren’t natural tool users and their beaks are too curved to wield sticks with grace.

It’s not surprising then, that the crows were more adept than the keas at using the sticks to reach their food. All the crows managed it; of the keas, only Kermit did so with his complicated technique. The crows’ fondness for sticks didn’t always work to their favour. They would often try to poke the window with their sticks, while the keas soon learned to pull them open using handles. Even when Uek did lift the window, she still prodded at the food with her stick when she could have just stuck her head through.

These are all captive animals that have taken part in various experiments before (although nothing quite like the puzzle box). Still, Auesperg expects that their behaviour would mirror that of their wild cousins, and says that several studies are now being done with wild birds.

In the meantime, these results clearly show that while both birds are capable of impressive feats of problem-solving, but react differently to the same task. They’re influenced by their anatomy: crows have straight bills but keas have curved ones. They’re influenced by their predispositions: keas like new things, crows shy away from them. They’re influenced by their environment: keas dig haphazardly for food, crows are used to precise prodding. An animal’s mental skills don’t evolve in a vacuum – they are tailored to that species’ body, lifestyle and environment.

This means that it’s hard to say anything about general skills such as problem-solving, memory or self-awareness based on an animal’s performance at a specific task. It’s important to use a battery of tests, such as the four “solutions” to Auesperg’s puzzle box. Even then, an animal’s performance may depend more on its attitude to novelty, motivation or body shape than its mental abilities.

Auersperg’s study is a breath of fresh air. It appreciates that “intelligence” looks very different from species to species based on their evolutionary context. Rather than simply ranking her birds against one another, she catalogued the differences between them and looked at why those differences exist. These are more interesting questions than the bland one of which one’s “better”.

PS Uek has a distinguished pedigree. He’s the son of Betty, a famous New Caledonian crow who has distinguished herself in several past experiments, including one that showed how these birds can combine tools.

Reference: Auersperg, von Bayern, Gajdon, Huber & Kacelnik. 2011. Flexibility in Problem Solving and Tool Use of Kea and New Caledonian Crows in a Multi Access Box Paradigm. PLoS ONE http://dx.doi.org/10.1371/journal.pone.0020231