Rooks and Crows

Aesop was quite the fable-teller, but was he a student of bird behavior as well? A study in Current Biology suggests he might have been. Christopher Bird of the University of Cambridge and Nathan J. Emery of Queen Mary University of London report that rooks, a relative of the crow, are able to use stones to raise the level of water in a container so they can reach a floating worm. If that sounds familiar, it’s because it’s similar to Aesop’s fable about the crow and the pitcher, in which a thirsty bird adds stones to raise the water level in a pitcher in order to drink from it. Crows, rooks and other corvids are known for their tool use — using sticks as probes, for example, or fashioning hooks out of wire. Dr. Bird, who studies corvid behavior, knew of a 1980s study in which a rook plugged a hole in its aviary to allow a pool of water to form. That led him to wonder if a corvid could do what is described in the fable.

They experimented with four captive rooks, presenting them with a clear tube partly filled with water with a bug floating on top, and a pile of stones. In one variant, the starting height of the water changed from trial to trial. In another, the birds had a choice of two sizes of stone. The birds quickly caught on, and within a couple of trials had figured out how many stones they needed to bring the bug within reach. “It was a remarkable combination of some understanding of the task with really rapid learning,” Dr. Bird said. The findings were published in Current Biology. Rooks don’t use tools in the wild, because they don’t need to — they have easy access to food like carrion. But in captivity, they can be presented with a situation like this, where it pays to figure out how to perform a task. “This fits nicely with Aesop’s moral,” Dr. Bird said, “that necessity is the mother of invention.”

The researchers suggested that Aesop (or whoever came up with the fable, since the stories are thought to have many origins) may have seen similar behavior in a crow. Or perhaps, Dr. Bird said, it was a rook. “In folklore all members of the corvid family are just called crow,” he said. “So it might just as easily have been Aesop’s rook.” *New York Times