What he is at the time of the sangava, that is the âdi, the first, the Om. On it birds are dependent. Therefore birds fly about in the sky without support, holding themselves, for they share the âdi (the Om) of that Sâman.

In plain words: The sun in mid-morning is the 'first' part, linked to Om, and birds belong to it. That is why birds can fly in the sky with nothing holding them up.