One Bharat Bhushan, uploaded the book "Birds of the Ramayana - Kakabhushundi", at
In the notes, it is claimed that Kaaka bhushunDi RaamaayaNa is the oldest of the Ramayanas.
Notes :The Birds of the Ramayana is a series that presents the most prominent bird-characters associated with the Ramayana. The Kakabhushundi Ramayana is attributed to the sage who had the body of a crow, cursed and blessed by Shiva to be always with devotion to Rama. It is thus written that Kakabhushundi, the sage who was reborn as a crow, was the first one to narrate the Ramayana, much before Valmiki or Shiva or Tulsidas. There are various versions of the Ramayana. Devotees through many centuries are familiar with the Valmiki Ramayan, written in verse form by the Sage Valmiki, and the Ramacharitamanas, written in near-contemporary times by the devotee-poet, Tulsidas. Not many devotees are familiar with the Adhyatma Ramayana that was narrated by Shiva to Parvati, much earlier than the Valmiki Ramayan. It is said that the Ramayana narrated by the sage-crow, Kakabhushundi, now known, as the Kakbhushundi Ramayan was much earlier to the Adhyatma Ramayana. It is also strange that the Kakabhushundi Ramayana does not seem to find a prominent place in the scriptures. Was it perhaps due to a hidden class system that desired the author of each scripture and the prominent deity to be considered more important? This is also almost true of the Adhyatma Ramayana, for one cannot ascribe a human author to either. Who did actually write these first of the Ramayanas? Was the aspect of Kakabhushundi entirely metaphorical for a human devotee who did not come from the prominent communities? We would never know. There are several theories and discussions in this regard. The vedas, upanishads and puranas are equal in explaining that knowledge is supreme in placing the written word above the thought or form of the deity. Perhaps, it is this fallacy that the sage-crow Kakabhushundi sought to demolish by explaining to Garuda, that devotion alone is supreme, and real. The rest is illusion.