Apteryx owenii occurred in forested areas throughout New Zealand prior to European settlement, but is now restricted to five offshore islands to which it has been introduced, and one mainland site where it has been reintroduced7. The stronghold is Kapiti Island (20 km2), where birds are believed to have been introduced in the early 1900s. In the 1980s, birds were released on Red Mercury (2 km2), Hen (5 km2) and Long Islands (2 km2), and to Tiritiri Matangi Island (2 km2) in 1993 and 19951. The population is estimated at 1,150 individuals (2000)8, with c.1,000 on Kapiti, 50 on Hen, 15 on Tiritiri Matangi, 30 on Red Mercury, 10 on Long Island, a number at Karori Sanctuary (Wellington) and 10 in captivity2. The populations on the smaller islands are expected to grow further6. On Kapiti, the proportion of juveniles in the population appears to be very high5 and annual survivorship is estimated at 97.5%8; numbers may have reached carrying capacity6.