It turns out crows aren't the only birds with fiendishly powerful memories. Pigeons are also capable of spontaneously remembering which humans mistreated them, and even an attempt to disguise the identity of their one-time abuser can't fool them.
Thankfully, pigeons aren't as mean about all this as crows, who are known to hold five-year grudges. But once a pigeon recognizes a human as a threat, it appears there's no way of convincing them otherwise. That's the takeaway from experiments conducted by researchers at the University of Paris. The team worked not with laboratory-bred captive pigeons, but instead with feral birds who had received no special training or instructions. Despite this, the pigeons displayed an amazing aptitude for recognizing human faces.
Here's the experiment that the researchers conducted. Two similar-looking humans would go to a park. One person would ignore the pigeons completely, while the other would actively try to chase them away. Then the pair would return to park, but this time neither would bother the pigeons. The researchers repeated this several times, on some occasions even having the two humans swap clothes so as to confuse the pigeons, but the birds always immediately recognized with human had once mistreated them and without fail ran away from that person.
Dr. Dalila Bovet explains what this means:
"It is very likely that the pigeons recognised the researchers by their faces, since the individuals were both female and of a similar age, build and skin color. Interestingly, the pigeons, without training, spontaneously used the most relevant characteristics of the individuals (probably facial traits), instead of the lab coats that covered 90% of the body."
This ability is quite possibly a modern development to pigeons living among humans in cities and other areas. Since humans possess so much control over the pigeons' preferred habitat, it makes sense that the birds would have developed a basic ability to recognize which humans are potential threats.