If there's a reason that Jiehae Park's play "the aves" is presented with a lower-case title, it's probably not because all the birds in the world are contained in its two-word classification. Rather, "the aves," now receiving its world premiere at Berkeley Repertory Theatre, is a low-key experience for musing on life, death, youth, age, love, loss and, yes, birds. Pigeons and doves, mostly.