Why do birds sing

One early discovery was that there are several tiny areas within the brain that are dedicated to singing. These regions are much larger in males (who typically do all, or most, of the singing) than in females. They are larger in bird species like the shaliks, that learn elaborate songs, than in birds like sparrows that can only learn a simple song. And within a species like the doel (Magpie Robin) these brain regions are larger during the seasons in which the birds are singing than in the other seasons.

How does this happen? Step by step, Dr. DeVoogd and other biologists are putting answers together. In baby birds these song production areas are alike in males and females. However, brain cells in these areas die in young females, thereby creating a difference in song production areas that will remain part of their brains throughout their lives. When a young male is one or two months old he listens to the songs of his father and of other adult males and memorizes many of the sounds that he hears. Later, he begins to put together his own songs using these notes. In males of most species this is the song that he sings every spring as he tries to attract a female, or warns other males to stay away.

A female, in turn, listens to these songs. In many species a female compares the songs of different males and chooses to pair and mate with the one whose song is most attractive. Often, it is the male who has learned the most and has the stamina to keep singing and singing. As females keep choosing males with the best songs, and generation follows generation, gradually the males sing better and better songs -- the influence of genetics coupled with enhanced learning -- until, ultimately, the males not only thrill the females but enchant us as well.

How does the brain carry out these tasks? Nerve cells or neurons bring information to the brain, carry information from one part of the brain to another, and carry the signals that instruct muscles to move. Dr. DeVoogd and colleagues have found that each of the events above is caused by changes in neurons or their connections (synapses). If males are raised by females and never hear or learn a song neurons in a major song production area only grow about 80% of their normal quota of synapses. In adult males the male hormone testosterone rises in the spring. It makes the males interested in mating, and also causes neurons throughout the song production areas to grow many more synapses that are then lost when the breeding season is over.

Parallel changes happen in the brains of females. If they are raised without hearing a song they are not able to distinguish between good and poor songs as adults, and they have fewer synapses in the brain area used for song perception. Thus, learning creates synapses and these novel connections between neurons encode the learning and allow males and females to express it, each in his or her own way. Birds from species with more elaborate songs have more neurons in these areas to begin with, and so can form many more patterns of connections between the neurons than is possible in birds that only sing simple songs. The beauty of the biology inside the head matches the beauty of the behaviour.

Is study of bird brains simply an esoteric pursuit with no connection to humans? Dr. DeVoogd believes that there are close connections. Our brains, like those of birds, are composed of neurons and synapses. Our brains also change patterns of connection between neurons to register and store the things we learn. In fact, our brains use similar regions when we learn skills that require practice, such as riding a bicycle, playing a musical instrument, or speaking a language. In birds we can study the mechanisms that direct changes in synapses in detail. And even when observing particular molecules that are used in communication between neurons, or in modifying neuronal connections in the brains of birds, the findings in birds match closely with what is found in humans.

Such observations hint that the essential actions carried out by the brain are deeply alike, whether in a bird, or a tiger, or a human. So when you next notice a bird singing think about what is going on in his mind (as well as the minds of any females who are listening), and think as well of the kinship between you both that extends all the way to the molecules being made and used in his brain. And if you are a poet (or a lover) you may wonder whether the birds hear not just sounds that reflexively cause actions, but know beauty, too.

Rokia Afzal Rahman is Chairman, The Daily Star.