Birds are smart because they have compact brains
A bigger brain does not always mean a smarter brain. For example, elephants have much larger brains than humans, but much of their brain space is needed to control their colossal body, and not their information processing capacities. When comparing brains of different species behavioral biologists often use relative brain size: this is brain size corrected for body mass. On the relative scale humans, dolphins and great apes score higher than the elephant.
How about birds? Birds have large wings but a light body and walnut (or peanut) sized brains. However, they do have the reputation of being pretty smart. This holds not only for singing birds that produce amazingly complex songs, but also corvids (members of the crow family) and parrots. Corvids are clever in using instruments like little hooks to obtain food. Magpies successfully pass the mirror test, a test of self recognition used in research of cognition in babies and higher mammals. The African grey parrot is very clever in understanding numbers and concepts: the legendary grey parrot Alex (see picture) trained by Irene Pepperberg, a lecturer at Harvard University is a good example.
These avian capacities must have resulted from the unique adaptation of their brains to the environment during evolution, resulting not in brains that are larger (and also heavier) but lighter and with a more efficient architecture*. Now how can a tiny brain be so smart? A recent study published by the research team of Pavell Nemec** from Prague sheds some new light on this interesting problem. They compared the brains of different mammals and birds with the same brain size. They found that bird brains have more neurons (nerve cells) than mammalian brains and even primate brains of similar mass. So it’s not de brain size per se that determines smart or intelligent behavior, but the density or the number of nerve cells packed in certain areas of the brain. Avian brains seem to consist of small, tightly packed neurons and, importantly, many of these neurons are located in the forebrain, the area that is connected with cognition in humans. They also found that parrots and corvids have forebrain neuron counts equal to or greater than primates with much larger brains.