Very imaginative interpretations. My own guess is that the seven notes came from human speech as the octave corresponds to the range our voice traverses normally to encompass the range of expressions or rasas. Also the notes as they are spaced have an inbuilt musciality in juxtaposition. It is interesting instruments across the globe have their music anchored in the seven notes, without the benefit of corresponding tropical animal sounds.
By the way I encountered an amusing Australian bird who came and sang in 4 notes..Very musically gifted indeed.Sure he would even have named the raga had he come down to the Dec. Vizha.
Here is a version which is analogous to our RTP:http://www.youtube.com/watch?v=KfaplSc5ieM&sns=em