Birdsong is a magical language spoken by Mystical Creatures that can also be learned by other races. Birdsong can be understood by any sentient creature and is a true universal language. The same mechanics that make it work are employed, on a much cruder scale, by the Optical voice developed by the Gudersnipe Foundation. The Foundation likewise used a similar principle to create a universal translator. Birdsong can best be described as 'organic binary': it bypasses normal comprehension and is perceived directly by the speech center of the brain.
The only species that speaks Birdsong natively are the Unicorns, though dragons can learn it. This is due to the unicorns' experiential genetic memory, which provides each unicorn with the knowledge and experiences of every unicorn before it. Dragons, meanwhile, understand the principle through their own genetic memory and can communicate with it, but lack the ability to understand other languages they have not learned.
There allegedly exists a written form of Birdsong which, although inscribed on non-magical materials by non-magical means, somehow preserves the enchanted nature of the tongue allowing anyone who looks at it, to read it. Similar to the spoken form, the viewers must have the ability in some form to read, even if only their own native tongue.
Birdsong existed during the Mythical Age and was a true universal language. The incident at Babylon threw a spanner in the works, but the language still existed. Scholar may be a derivation; but as Birdsong is inherently magical, it is difficult to compare the two.