by William Swainson, Zoological Illustrations — Vol II. Pl… (1820)
“ The figures are of the natural size, the upper representing the female, and the lower the male bird: the head of the former is entirely destitute of the crest which distinguishes the latter; in every other respect the resemblance is uniform. This crest, when not erected, is concealed, being nearly covered by the olive feathers around it. When erected, however, it discloses a stripe down the middle of the head of deep straw-coloured feathers, some of which are tipped with olive. The upper mandible of the bill is triangular, and much hooked, notched, and depressed ”
