Page:Natural History, Birds.djvu/188

Rh beaks, these birds lightly traverse the branches of the forests and leap from one to another till the highest is attained: they then often stop and utter a loud roaring sound, which may be heard at a considerable distance..... The noise thus uttered, and which is most probably their call-note, throws a light upon the design of the hollow protuberance surmounting the bill; it acts as a sounding-board, increasing the reverberations of the air. With regard to the huge beak itself, many conjectures have been entertained as to its peculiar uses. It has been suggested as a reason for its development, that it perhaps constitutes a necessary weapon of defence against monkeys and other animals, which may seek to assail its nest; while some have supposed that it might be employed in dragging snakes and lizards from their lurking places, or young birds and eggs from the recesses of the trunks of aged trees."