Roosters were shown their reflections in mirrors and then were shown images of predators. If they issued a warning call it would indicate that a cock believed the mirror reflection to belong to another rooster. But if it recognised the reflection as its own, it would remain silent
A team of neuroscientists and psychologists from the Institute of Agricultural Engineering at the University of Bonn, and the Institute of Cognitive Neuroscience at the University of Bochum, both in Germany, has found possible evidence of roosters passing the self-recognition test. In their paper published in the open-access journal PLOS ONE, the group describes experiments they conducted with roosters and mirrors.