Crows Crack Geometry: These smart birds can tell squares from rhombuses, study says

New research suggests birds understand shape rules like humans do. (Image: Canva)

Crows might appear like they only screech and steal food, but scientists recently discovered a complex side of these clever birds. Like us, they recognise unfamiliar shapes.

German researchers found that carrion crows are sensitive to geometric regularity. They know when something doesn't quite fit. It was previously thought that this ability existed solely in humans.

Pattern recognition apart from further training
Andreas Nieder and his team conducted the study. Two mature male crows, ten and eleven years old, were used in their research. The experiment was conducted at the University of Tübingen. A computer monitor presented five geometric shapes to the birds. There was a single geometric shape that was different from the others. The unusual one had to be pecked out by the birds.

The crows had learnt this basic ability from past training, but they had never before encountered only quadrilateral shapes. This ensured the test measured natural, not learnt, behaviour.

The more symmetrical the quadrilaterals, the easier crows spot the odd one out. (Schmidbauer et al., Sci. Adv., 2025)

Different properties of two-dimensional quadrilaterals were used by the scientists. Rectangles and squares were some of the regular ones. Others were asymmetrical and looked like odd four-sided figures or rhombuses.

Crows did better when the forms were more symmetrical. They quickly selected the odd one when sides and angles were equal. They struggled more with irregular or asymmetrical shapes. Rhombuses were especially difficult for the birds, Nieder said. In a news release, he stated, "Just like humans." That suggests that their capabilities are closer to ours than expected.

Evolution-based instinct
Researchers added plain trials to maintain the interest of the crows. These presented known shapes, like stars and moons, to the birds. This prevented stress and boredom.

Their performance indicates a natural understanding of geometric principles. In order to recognise the odd shape, the birds did not need any further training.

"Birds use spatial patterns to navigate and survive," stated Nieder. This skill can assist them in navigating their surroundings in a safer way.