Measurements, plumage and moult of Red-crowned Parakeets (Cyanoramphus novaezelandiae novaezelandiae) were recorded during a banding study on Aorangi Island, Poor Knights Islands, between 1978 and 1986. Males were significantly larger than females in all measurements and in weight. Weight varied throughout the year and was highest in May and lowest in November. The weights of males was significantly less during October and November than at other times of the year, but there were no significant variations in the weight of females. More males than females were caught, and recaptures suggested that females had a lower survival rate than males. Two of the 329 parakeets banded had plumage characteristics of Red-crowned x Yellow-crowned Parakeet (Cyanoramphus auriceps auriceps) hybrids. Casual observations indicated that the breeding season extended from late October to January. Most birds were in active moult by late February.