Call a bird "birdbrained" and they may call "fowl." Cornell University researchers have proven that the capacity for learning in birds is not linked to overall brain size, but to the relative size and proportion of their specific brain regions.
Songbirds with upper brain regions that are larger in relation to lower regions have a greater capacity for learning songs. Higher brain areas control the majority of cognitive and learning functions, while lower brain areas control more motor functions, according to the new study published in the Proceedings of the National Academy of Sciences.
The research shows that when a bird's higher cortex-like brain area called the high vocal center (HVC) is larger relative to the lower brain area called RA, or if the RA is large relative to an even lower area called N12, the species is able to learn dozens of different notes. Such species as mockingbirds, catbirds, European blackbirds and European warblers can learn hundreds of notes because they have those relative size differences in both sets of areas.
"HVC size by itself only modestly predicts capacity for song learning, but relative size is a very strong predictor," said Tim DeVoogd, professor of psychology and of neurobiology and behavior and the paper's senior author. Jordan Moore, a graduate student in DeVoogd's lab, was the paper's lead author. "Our work is the first to demonstrate a basic principle of evolution using a specific behavior having greater cortical control of brain function gives greater behavioral flexibility, including enhanced learning."
In bird species with great capacities for song learning, higher brain areas likely became built up over lower areas as a result of sexual selection, he said, where females mated with males that had more elaborate songs. Repeated over millions of generations, the structure of the brains of these species changed such that higher brain areas became larger relative to lower areas.<
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