Age and sex determination of the Maui Parrotbill

We determined the best plumage and morphometric variables for ageing and se xing the Maul Parrotbill (Pseudonestor xanthophrys), an endangered Hawaiian honeycreep er found only on east Maul, Hawaii, by examining and measuring 30 museum specimens and 71 live birds captured in mist nets. Juvenal plumag e was identified by the presence of pale-tipped wing bars on the middle and greater coverts, grayish olive dorsal plumage, and dingy white underparts and superciliaries. Birds undergoing first prebasic molt retained the juven al remiges, rectrices, and wing coverts. Birds in first basic plumage posse ssed juvenal wing bars and a dull juvenal-like plumage. Subsequent molts we re complete, and adults lacked wing bars. Adult males had bright yellow plu mage on the cheeks, throat, and superciliaries, as did 27% of adult females . All other adult females had less yellow in the underparts. The dorsal plu mage of adult females was more variable than adult males and was either yel low-olive like the males or grayish olive. Adult males had longer wing, bil l, tail, and tarsometatarsus and greater mass than adult females. Virtually all males and females could be distinguished by wing length. Morphometrics of immature birds were significantly smaller than for adult males. Only im mature male wing chord was significantly larger than that of adult females. Although it was difficult to distinguish between immatures and some adult females based on plumage coloration or measurements, a cut-off point of 70. 4 mm for wing chord separated 91% of females from 93% of males, regardless of age.