Scientists studying the behavior of rooks in experiments at Cambridge University have shown that Aesop’s fable about a thirsty crow raising the water level in a pitcher by dropping stones into it may have had some basis in fact. Christopher Bird of Cambridge and a colleague, Nathan Emery of London University, showed three rooks a 15-centimeter plastic tube containing water with a worm floating on the surface. In the experiment, the results of which were published in the journal Current Biology, the rooks dropped stones into the tube to raise the water level, quickly learning that large stones did the job faster. Aesop, a Greek who lived in the 6th century BC, is recognized as the author of fables, mostly about animals, that were used as moral lessons, such as the race between the tortoise and the hare, the goose that laid the golden egg and the ant and the grasshopper. In a previous experiment, according to Alex Taylor and Russell Gray of the University of Auckland in New Zealand, the same birds had dropped a single stone into a tube to get to food at the bottom. However, they were able to work out that multiple stones were needed the second time in order to raise the water level. «This suggests that they can not only think through complex problems requiring the use of tools, but imagine the consequences of their actions without trial-and-error learning, and create novel solutions to these problems that have never been encountered before,» said Emery. In earlier experiments, the same group of rooks made a simple tool out of wire to help them get at food in a container. Rooks, like crows, were already known to use tools in previous experiments. The researchers said the crow referred to by Aesop may in fact have been a rook, since both birds were called crows in the past.