Study finds why birds sing in spring

It's a research which can shed new light on seasonal depression in humans -- birds know to sing during spring because of "hormonal changes" triggered by longer days. A team of international researchers has traced the changes in the bird's brain -- they have found that cells near the pituitary gland release a hormone during spring in readiness for attracting mates.

According to lead researcher Prof Peter Sharp of the Roslin Institute in the United Kingdom, "While we knew what area of the brain was affected by seasonal change, until now we did not know the exact mechanism involved.

"Now we have identified a key element in the process of the brain's activity when spring arrives. Such knowledge would have been impossible in the past but advances in technology enabled us to scan thousands of genes so we could work out which ones are affected by seasonal change." The team used a special gene chip -- known as a microarray -- to scan 28,000 genes from Japanese quail, which had received varying lengths of light corresponding to short and longer days.

They found that genes in cells on the surface of the brain were switched on when the birds received more light. The result was that cells started to release thyroid stimulating hormone called thyrotrophin.