Researchers have shown that pigeons have remarkable perception. They went to a park and had one researcher ignore the pigeons, while the other was hostile and chased them away. Then later, they each returned, and neither tried to chase them away.
The results were staggering: the pigeons ran away from the person who chased them away earlier, but not from the other one. They even recognized the people correctly when they switched their clothes. They were able to recognize their faces!