Turns out that crows are as smart as Aesop claimed:

Aesop had the measure of crows.

In his fable, there was a wise old mother crow who finds a pitcher with only a little water in it.

Desperately thirsty, the intelligent bird drops small stones into the container, raising the water level until it is high enough for her to drink.

The story might be 2,500 years old, but the Ancient Greek author clearly understood how the crow’s mind works.

For when we recreated the experiment in our laboratory in Cambridge, the birds did exactly as Aesop described. Without being taught the details of the task, they picked up stones and dropped them into a tube of water — raising the water level.

This experiment is part of a research programme which has proved that members of the crow family, known as corvids, aren’t just among the cleverest birds, they are smarter than most mammals.

In fact, their intelligence rivals that of apes — who, along with crows, are able to do tasks that three and four-year-old children have difficulty with.

They also have a theory of mind, and can plan ahead.

These findings have fascinating implications.

People used to believe that the high level of intelligence we see in humans and apes evolved only once on the planet, but if it occurs in distantly related groups — the common ancestor we share with birds lived 300 million years ago — it suggests this intelligence evolved more than once.

This means that we may have other intelligent lifeforms on earth that we are not aware of. And because birds’ brains are very different from mammal brains, it raises questions about what kinds of brains support intelligence.