Stone the crows: bird brains soar to top of the class

CROWS, rooks and jays may have bird brains but they can think like chimpanzees and humans, scientists said yesterday.

Researchers who reviewed studies of crow intelligence concluded that they had separately evolved the same kind of mental abilities as higher primates.

Crows belong to the family of corvids, which also includes rooks, jays, ravens and jackdaws. They have brains significantly larger than would be expected for their body size. In relative terms, a crow’s brain is as big as a chimpanzee’s.

In folklore, the corvids are credited with high intelligence. One Aesopian fable tells of a thirsty crow that placed stones in a pitcher containing water until the liquid’s level was high enough for it to reach.

Yesterday’s review by two animal behaviour experts at Cambridge University suggests that there might be more than a grain of truth in such stories.

Research showed crows and their relatives were amazingly skilled at making and using tools, and demonstrated the kind of social interactions normally seen in primates.

They were able to remember the “what, where and when” of activities such as hiding food for later consumption. And like apes, they used a combination of mental tools - including flexibility, imagination and the ability to anticipate possible future events - to form a complex view of the world.

Nathan Emery and Nicola Clayton wrote in the journal Science: “There are many aspects of corvid and ape cognition that appear to use the same cognitive tool kit: causal reasoning, flexibility, imagination, and prospection. We suggest that nonverbal complex cognition may be constructed through a combination of these tools.”

One captive crow, Betty, astonished scientists by modifying a metal wire into a hook, to retrieve food from a vertical tube.

Furthermore, she chose the correct length and diameter of wire out of a “toolbox” containing different-sized objects.

Pilfering of other birds’ food supplies was common, and corvids had developed ingenious strategies to outwit thieves. Examples included hiding food behind barriers, waiting until pilferers were distracted before concealing food, leading potential thieves away from cache locations, and making false caches that contained either inedible items like stones or nothing at all.