Canary-lovers know that their pets can warble a lullaby one year but may sing a waltz-like tune the next. It has long been known that a canary's song may vary from year to year, but not why or how this can be.
Fernando Nottebohm, a Rockefeller University ethologist, conducted studies of more than a score of male canaries' songs at the institution's field research station in Millbrook, N.Y. He then correlated their changing song repertoires from year to year with the size of the two parts of their brains that appeared to govern their song output.
He found that when they were in their most productive song period, usually in the winter, those two parts of the brain were up to twice as large as during the birds' least productive period during the summer molt, when the brains shrank and the nerve fibers became smaller.
But when the brain parts grew larger in the fall, new nerve fibers developed and formed new synapses, connections between nerve cells, that led to new tissue growth in the vocal control nuclei in the canary's brain, enabling it to produce a new song repertory.
Dr. Nottebohm, whose research is reported in the Dec. 18 issue of Science, reasons that if a bird's brain can be ''rejuvenated'' in such a way, it may possibly occur in other animals.
He found that when they were in their most productive song period, usually in the winter, those two parts of the brain were up to twice as large as during the birds' least productive period during the summer molt, when the brains shrank and the nerve fibers became smaller.
But when the brain parts grew larger in the fall, new nerve fibers developed and formed new synapses, connections between nerve cells, that led to new tissue growth in the vocal control nuclei in the canary's brain, enabling it to produce a new song repertory.
Dr. Nottebohm, whose research is reported in the Dec. 18 issue of Science, reasons that if a bird's brain can be ''rejuvenated'' in such a way, it may possibly occur in other animals.
