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McGill University researcher Evan Balaban performs brain transplants on chickens to make them sing like quails. He takes bits of brain from quail embryos and attaches them to the brains of embryonic chickens still snug in their eggs.

When they hatch, the chickens look normal, except for the dark, quail-coloured feathers sprouting out of their heads. But they do not sound normal. Instead of crowing the classic cock-a-doodle-doo, they sing the two introductory notes and the long trill of a quail song.

"They actually sing like quails," he said.

Dr. Balaban, who recently moved to Montreal's McGill from the United States, is not trying to create feathered Frankenstein monsters. His chimeras, as the quail-chicken combos are known, are a tool for learning how brains are programmed to play a role in particular behaviours.

What makes roosters crow and quails sing?

In the past, researchers believed that birds learned their songs from their parents and other birds in their communities.

But studies have shown that bird brains appear to be hardwired to learn the songs of their own kind. Baby birds hatched in a laboratory and exposed to recordings of the songs of more than one species learn and retain their own songs at a much higher rate.

The same process may be at work with human infants, who even as newborns are attracted to the sounds of speech. No one understands how this works.

Dr. Balaban and his colleagues decided that brain transplants were a good way to find out. He does not believe the surgery, as it is now performed, would work in humans. In the future, however, it may help surgeons use donor cells from other species; for example, grafting brain cells taken from pig embryos to the brains of people with neurological disorders such as Parkinson's disease.

Dr. Balaban spent 12 years perfecting the chicken-to-quail brain transplant. He is establishing his new lab, and soon will be teaching graduate students in Montreal how to perform the surgery.

Using a wee pair of scissors, he cuts tiny windows in the eggshells. Then he switches to micro-scalpels made out of stainless-steel wire he sharpens under a microscope. He removes chicken brain cells and replaces them with quail brain cells.

By the process of elimination, he and his colleagues in the United States identified a small group of cells that made quails sing like quails. The scientists have also isolated the cells responsible for the bobbing head movements that quails make when they sing, and even for a particular, frantic sound quail parents make when warning their offspring of danger.

Chicken brains are bigger, so it is easier to perform the brain transplants on them. Chickens normally have white or yellow feathers. They sprout black and brown quail-coloured feathers because the transplant includes cells that determine the skin and feather pigmentation.

After the surgery, the chickens hatch and grow for two weeks before their bodies reject the quail cells.

That gives Dr. Balaban little time to figure out what is going on. He has not detected many physical differences between the quail brain cells and the chicken brain cells. The two birds, after all, are closely related.

But he is hoping that high-resolution brain-imaging equipment, designed specially for tiny animals, will help him understand what happens after the transplant, but before the birds hatch. He uses the scans to compare normal chicken brains with those that have had the transplant.

There are indications that the quail song is not embedded in the quail brain cell like a computer chip; change the chip and you change the song. It is more complicated than that. The quail cells seem to send out signals, chemical cues that tell the embryonic chicken brain to build a particular circuit of cells responsible for the quail song.

He is hoping to learn how the quail song circuit is connected to the rest of the brain, and how long before hatching can the brain tell the difference between songs.