Self-recognition was long believed to be unique to humans. However, it was established more than 30 years ago that the great apes are capable of recognizing themselves in the mirror, and more recently it has been found that dolphins and elephants can too.
Now Prior et al provide the first evidence of mirror self-recognition in a non-mammalian species. In this film clip from the supplementary materials which accompany the paper, a magpie (which is actually a female) realizes that it has a mark on the side of its head after seeing its relection in the mirror. It then removes the mark by rubbing its head on the ground, and finally looks in the mirror one more time to make sure the mark has come off:
Birds lack a neocortex, the layered structure which is specific to mammals and which in humans is responsible for everything that we consider unique to our species. But even with their smooth, non-layered brains, birds are still capable of highly complex cognition. The Clarke’s nutcracker has remarkable spatial memory – it can cache nuts in tens of thousands of different locations, and retrieve them all as winter closes in; and crows have tool-making and using abilities that are at least as sophisticated as those of chimpanzees.
Such abilities are associated with a structure in the avian brain called the nidopallium caudolaterale, which corresponds to the mammalian prefrontal cortex not just functionally but also neurochemically (it uses the same, or similar, neurotransmitters). Thus, during their separate evolutionary histories, selective pressure has led to the emergence of complex cognition in both birds and mammals. This is an example of convergent evolution – the same abilities have evolved independently of each other, in two very different groups of organisms with very different brains.
Prior, H., et al (2008). Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition. PLoS Biology 6 (8): e202. DOI: 10.1371/journal.pbio.0060202