March 20, 2008

Scientists Discover Why Birds Sing in Spring

Japanese and British researchers reported Wednesday that birds begin singing during the spring season as a biological response to longer days. The response, said researchers, is a result of hormonal reactions to brain cell triggers that tell the birds to find mating partners, which they do through singing. 

"While we knew what area of the brain was affected by seasonal change, until now we did not know the exact mechanism involved," said Peter Sharp, a Roslin Institute researcher, who took part in the study.

The research was led by Nagoya University's Takashi Yoshimura. The team examined 38,000 genes in Japanese quail brain samples to determine which ones were affected by varying degrees of light. 

The researchers discovered that genes in cells on the surface of the brain turned on in response to more light and the birds then began releasing a thyroid-stimulating hormone. The study showed that the genes activated 14 hours after dawn on the first day of sufficient length, said researchers.

"Such knowledge would have been impossible in the past, but advances in technology enabled us to scan thousands of genes so that we could work out which ones are affected by seasonal change," Sharp said in a Reuters telephone interview.

The thyroid-stimulating hormone, previously associated with growth and metabolism, stimulated the pituitary gland to secrete other hormones, which in turn caused the birds' testes to grow, which made the birds crow in attempts to attract a mate.

Sharp said the study's findings could one day lead to better infertility treatments, since humans have the same cells in the same part of the brain.

"It is sitting there and standing there with the same characteristics as in birds," he said. "The big question is whether these cells are involved in the reproductive system."

The study was published in the journal Nature. 

A summary can be viewed at http://www.nature.com/nature/journal/v452/n7185/abs/nature06738.html.