Tuesday, February 06, 2007

Bird Brains -- On Corvid Intelligence

Over at the Neurophilosophy blog, there is an outstanding post on the intelligence of various members of the corvid family (crows, ravens, jays, and rooks). I have long been a fan of crows and ravens, as you might guess from the icon I use in the "about me" block. The entry includes video of crows solving problems, which I had seen before but I always enjoy seeing again.

Here is a little of the post:
Earlier this year, members of the Comparative Cognition Lab, at Cambridge University’s Department of Experimental Psychology, published a study which shows that rooks use social interactions as a means of stress management. Like pinyon jays, rooks live in societies containing large numbers of individuals. Rooks are monogamous, and male-female pairs typically mate for life. Pairs do not fight with each other, but with neighbours, usually over food or nest-building materials. Amanda Seed and her colleagues filmed and analyzed the post-conflict behaviour of a group of 10 rooks, which included 4 monogamous pairs. They found that, although birds that come into conflict never reconciled with each other, they often sought solace in their partner afterwards, by sharing food, preening each other, and twining bills. Prior to the study by the Cambridge group, this behaviour had been observed in monkeys, but never in a non-primate.

Corvids are also capable of remarkable feats memory. Pinyon jays, for example, live in flocks of up to 500 individuals, and will determine their status within a dominance hierarchy by inference, rather than by direct interaction with other individuals, which is both time-consuming, and dangerous. The pinyon jay is able to recognize large numbers of individuals within their group, and to track social relationships over long periods of time.

The Clark’s nutcracker - another member of the Corvid family - displays an extremely accurate spatial memory. It is known to store around 100,000 pinyon seeds in 20,000-30,000 separate caches, which can be recovered up to 9 months later. Although exactly how the bird acheives this is unclear, the use of visual cues, particularly large landmarks, is known to be involved. Astonishingly, it was recently found that Western scrub jays use counterespionage methods to prevent their stored food caches from being stolen. If they are aware that they have been observed by a competitor while storing their food, they re-hide the cache so that the other bird loses track of where it is. This is evidence that they are able to infer the mental state of other birds and that, maybe, birds have a “theory of mind”.

Equally remarkable is the ability of some birds to adapt their behaviour to new circumstances. Crows are now known to be sophisticated manufacturers and users of tools. Crows also display ‘handedness’ - some hold the tools against their left cheek, and others hold them against the right cheek. The use of tools was previously thought to be restricted to humans and other primates. In the film clip below, a crow first tries unsuccessfully to retrieve food from a container using a straight piece of wire; it then bends the wire against the side of the container, to make a hooked tool, which it uses to retrieve the food:

(from the Behavioural Ecology Research Group at the University of Oxford)

Crows can use a variety of tools, and can also select the tool best suited to the task at hand. In one study, captured crows were presented with pre-made tools of different diameters and tubes containing food that was accessible only through a small hole. The birds were seen to select the most appropriate tool, which they then used to retrieve the food. Furthermore, if the tools were tied together in a bundle, the crows were still able to select the right tool after they had untied the bundle.

Crows can also design new tools when they need to. In the wild, Gavin Hunt and Russel Gray, of the University of Auckland in New Zealand, have observed crows crafting hooked implements from leafy twigs. first case of the crafting of tools by a non-human species. The crows manufacture the tools in three stages, each of which involves a complex manipulation of the materials being used. First, they select the appropriate raw materials; normally, this is a fork formed from two twigs. The side twig is then broken off just above the junction of the fork, and discarded. The other twig is then broken off just below the junction. Finally, the bird uses its bill to remove the leaves, and to sculpt a fine hook from the end of the twig:

(from the Gray and Hunt Laboratory at the University of Auckland)

Check out the rest of the post.

1 comment:

hderms said...

absolutely fascinating