There has been a range of opinions about sexual dimorphism in the Helmeted Honeyeater Lichenostomus
melanops cassidix despite little supporting data, yet these opinions have played an historic role in the definition
of the taxon. We demonstrate that males are, on average, larger than females in a range of characters, but
there is no absolute morphological distinction. We were unable to identify any consistent or marked differences
in plumage between the sexes. There are also few differences between the plumage of young birds and adults,
the only categoric difference being in the shape of the tip of the rectrices. However, juveniles have a yellow
gape, bill and palate whereas those of adults are black. Gape colour is the more persistent of the three juvenile
traits, but its persistence varies greatly between individuals. There are also differences between juveniles and
adults in the colour of the legs and eyes. In its age and sex characteristics, the Helmeted Honeyeater closely
resembles the inland race of the Yellow-tufted Honeyeater L. m. meltoni, notwithstanding large differences in size
and the intensity of plumage coloration.
