Physics-minded crows bring Aesop’s fable to life

Eureka! Like Archimedes in his bath, crows know how to displace water, showing that Aesop’s fable The Crow and the Pitcher isn’t purely fictional.

To see if New Caledonian crows could handle some of the basic principles of volume displacement, Sarah Jelbert at the University of Auckland in New Zealand and her colleagues placed scraps of meat just out of a crow’s reach, floating in a series of tubes that were part-filled with water. Objects potentially useful for bringing up the water level, like stones or heavy rubber erasers, were left nearby.

The crows successfully figured out that heavy and solid objects would help them get a treat faster. They also preferred to drop objects in tubes where they could access a reward more easily, picking out tubes with higher water levels and choosing tubes of water over sand-filled ones.

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Bird-brains solve problems spontaneously

In certain situations animals can spontaneously solve problems without planning their actions, according to research from The University of Auckland’s School of Psychology.

Animals rarely solve problems spontaneously, yet certain bird species are able to rapidly gain access to food hung on the end of a long string, by repeatedly pulling and then stepping on the string. For over 400 years it has been a mystery as to how the birds spontaneously solve the “string pulling” problem.

The University of Auckland research shows that such problem solving is not created by birds first solving the problem in their heads. Rather, problem solving occurs online as the bird makes the food on the end of the string move.

“Crows and parrots have long been known to solve the string pulling problem immediately. What our new research shows is that these performances are due to the birds being able to react in the moment to the effects of their actions, rather than being able to mentally plan out their actions,” says Dr Alex Taylor, lead author on the study.

“Thus string pulling appears to be based on a different type of intelligence than we had thought. Instead of the crows using sophisticated cognitive software to model the world, it appears their neural hardware is sufficiently well connected and/or specialised for them to react to the effect of their actions immediately. This allows them to solve problems that other bird species cannot.”

The work, by Dr Taylor, Brenna Knaebe and Professor Russell Gray, titled “An end to insight? New Caledonian crows can spontaneously solve problems without planning their actions”, has been published in the Proceedings of the Royal Society B: Biological Sciences online.

If two birds meet deep in the forest, does anybody hear? Until now, nobody did, unless an intrepid biologist was hiding underneath a bush and watching their behavior, or the birds happened to meet near a research monitoring station. But an electronic tag designed at the University of Washington can for the first time see when birds meet in the wild.

A new study led by a biologist at Scotland’s University of St. Andrews used the UW tags to see whether crows might learn to use tools from one another. The findings, published in Current Biology, supported the theory by showing an unexpected amount of social mobility, with the crows often spending time near birds outside their immediate family.

The study looked at crows in New Caledonia, an archipelago of islands in the South Pacific. The crows are famous for using different tools to extract prey from deadwood and vegetation. Biologists wondered whether the birds might learn by watching each other.

The results, as reported by St. Andrews, revealed “a surprising number of contacts” between non-related crows. During one week, the technology recorded more than 28,000 interactions among 34 crows. While core family units of New Caledonian crows contain only three members, the study found all the birds were connected to the larger social network.

The new paper is the first published study using the UW tags to record animal social interactions.

Why clever crow is no bird brain

Corvus moneduloides, a native of France’s South Pacific territory of New Caledonia, is one of the stars of the avian world.

It uses its beak to craft complex tools from sticks, leaves and other material and then inserts them into deadwood or vegetation to fish out insects and other food.

Researchers led by Jolyon Troscianko of the University of Birmingham in central England used an ophthalmoscope video camera to record field of view and eye movement as three wild-caught birds examined a baited tube.

The bird’s eyes are more forward-positioned, rather than sideways-positioned, which gives it exceptional “binocular overlap,” they found.

This is the area that is viewed by both eyeballs, and is important because it helps the brain judge the distance of nearby objects.

In New Caledonian crows, the binocular overlap is 61.5 degrees, which is at least 23.9 degrees greater than in non-tool-using species of crow that the researchers also examined.

Added to this is the crow’s unusually straight bill, the investigators found.

With it, the bird can get a firm grip on a tool and bring its tip into its field of binocular vision.

"These features enable a degree of tool control that would be impossible in other corvids [crows], despite their comparative cognitive abilities," says the study, published by the journal Nature Communications.

Dolphins, elephants and other birds are among non-primates that have been found to use tools. But the New Caledonian crow occupies a privileged place because its features are so specifically adapted for tools, says the study.