Morphometrics of the whiteheadMohoua albicillaon Little Barrier Island, New Zealand

Abstract

We measured 95 whiteheads (Mohoua albicilla) on Little Barrier Island, including 39 of known sex. Known males were significantly heavier and larger, on average, than females, although there was some overlap. Within mated pairs the male was always larger than the female. A plot of weight against wing length or a simple sum and product of four parameters, completely separated the known males and females and allowed most other birds to be sexed. Plumage and leg colour are only partly reliable as indicators of sex. All birds classed as males from their bright white heads and shiny black legs were subsequently found to be males. All females were successfuly classed as females from their duller plumage and paler legs, but so were many males. Comparison with published measurements of whiteheads from near Wellington suggests that there is no clinal variation in size. Whiteheads are intermediate in size between brown creepers (Finschia novaeseelandiae) and yellowheads (M. ochrocephala). Males are larger than females in all three species.