This is weirdly interesting to me as (a) a writer, (b) a curious human being, and (c) someone who's been drilling round / taking baby steps into formal linguistics, Saussure (ie the arbitrary nature of the connection between words and their meanings), etc in the last year or so...
So this is basically about how 'meaning' is generated / built-up from the semi-random / apparently meaningless blocks of information - how language seems to generate its own structure(s), not, "so, like, birds makes sounds that are like human ones", okay?
And in this example the evolutionary advantage for this process is fairly obvious.
(note: broken link from earlier now fixed)
"Although the two babbler bird calls are structurally very similar, they are produced in totally different behavioural contexts and listening birds are capable of picking up on this."
The authors report that in the chestnut-crowned babbler, the first sound element "B" is what seems to differentiate the meaning between flight and prompt vocalisations, akin to cat and at in English, where the c represents the meaning differentiating element, or phoneme.
"Although this so-called phoneme structuring is of a very simple kind, it might help us understand how the ability to generate new meaning initially evolved in humans," added Dr Simon Townsend. "It could be that when phoneme structuring first got off the ground in our hominid ancestors, this is the form it initially took."