Why every bird species sing their song differently?

A new study claims that every bird species learns to sing their song separately without being influenced by other birds in the proximity. As a bird expert, you may be able to tell the songbirds apart from their songs, but for others, the songs all seem similar. 
New research by the scientists at Hokkaido University, Japan, says that the songbirds don’t seem to be affected by other birds or each other. They learn their tunes a....