The world population is unknown; estimates for the size of the remnant population on Hauturu (Little Barrier Island) range from 600 and 6000 adult birds. There are also translocated populations on Tiritiri Matangi Island, Kapiti Island, Zealandia, Maungatautari, Bushy Park and Lake Rotokare. Attempts to establish populations on Hen Island, Cuvier Island and Mokoia Island and the Waitākere Ranges failed. Reintroduction to these new sites has created genetic bottlenecks that have reduced genetic diversity in the newly founded populations and led to inbreeding.