Estimating the population size of orange-fronted parakeets (Cyanoramphus malherbi) on offshore islands of New Zealand

Abstract

ABSTRACT Determining the size of translocated populations of endemic New Zealand species is essential for assessing their management requirements; however generating estimates can be constrained by the accessibility of sites, particularly for cryptic or difficult to monitor species released on remote islands. In this study, we aimed to produce estimates of population size for three translocated populations of the critically endangered orange-fronted parakeet (Cyanoramphus malherbi), after a mean establishment period of 6.3 years. We also recorded natural history notes of the species. Using fixed-point distance sampling, we assessed the populations established on Te Kākahu-o-Tamatea / Chalky Island, Te Pākeka / Maud Island, and Oruawairua / Blumine Island. We confirmed the presence of orange-fronted parakeets on Te Kākahu-o-Tamatea / Chalky Island but could not produce density estimates due to a small number of detections. We did not detect orange-fronted parakeets on Te Pākeka / Maud Island. On Oruawairua / Blumine Island, based on 20 detections, we estimated a population of 193 ± 91 parakeets distributed through the mature forest of the 3.77 km2 island. Our findings indicate that Oruawairua / Blumine Island sustains a significant population of the critically endangered orange-fronted parakeet. To assess the long-term trends of the species on offshore islands, further population assessments are needed.