In the journal Science Advances, the researchers describe a series of tests showing that crows clearly had a sense of right angles, parallel lines, and symmetry. Before these results, says Nieder ...

It is a closed 3-sided shape made up of straight lines ... equal angles, each measuring 60º. This means that this triangle is equilateral. You can also describe the angles as congruent ...

Continued testing showed that the birds had some understanding of right angles, parallel lines and even some degree of symmetry. The research team suggests their experiments were quite convincing ...