Phrase which the duck produces. this is a rediscovery, essentially, is it special, significant?— special, significant? yes, it is very special- _ special, significant? yes, it is very special. vocal _ special, significant? yes, it is very special. vocal learning . special, significant? yes, it isj very special. vocal learning in general is a rare trait among animals. we are the only primate species capable of doing it and for mammals, it is whales and dolphins and a couple of pet species. for birds, we know it from song birds, parrots and hummingbirds, which are three groups of about 40 bird...