From page 138 of Bird Brain:
Mirrors have been used in experiments with birds to test if they have a sense of self. Different species of birds react in different ways when confronted with their reflection. For example, flamingos will only mate when their flock is large enough—mirrors have been used to trick them into thinking it is. Various crows behave as if in the presence of another bird, with females preening and males displaying. New Caledonian crows use the mirror to forage for food that is not visible without it, suggesting that they know how it works. Magpies seem to recognize their own reflection, and use the mirror to preen parts of their bodies that were not visible without the mirror.
Birds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.
Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.
Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.