From the book

“We know them primarily by their deep, resonant croaks, of course, easily distinguished from the caws of crows . . . But there’s much more these ravens have to say. Female ravens ‘knock’ vocally much like female jays ‘rattle,’ thus revealing their ancestral relationships; sometimes it’s just two knocks in rapid succession, perhaps three, or perhaps a dozen within a second . . .”

In the first minute and a half of this recording from Mt. Hood, Oregon, hear this raven give three series of croaking sounds, the first and third seemingly the same kind of croak. Then, in a little over a half minute, this adult female gives six knocking sounds, sounding a little bit like a woodpecker drumming on a hollow tree.