ROLE OF PREDATION IN THE DECLINE OF KIWI, APTERYX SPP, IN NEW-ZEALAND

Kiwi have declined markedly in abundance and range since human settlem ent of New Zealand. Three of the four species are still extant in main land forests, despite decades of co-existence with various introduced mammals. Little spotted kiwi is now probably confined to offshore isla nds. The role of introduced mammals in these population declines was e valuated by measuring the survival rates of adults, eggs and chicks of brown kiwi (A. mantelli) and great spotted kiwi (A. haastii) in mainl and forests. Mortality rates of adults ranged from 5%-16% and did not differ significantly between species or sexes. Overall, 14 out of 209 adult kiwi died during 159.6 radio-tracking years. Predators definitel y caused five of these deaths. Sixty-nine (68%) of 102 eggs from 77 ne sting attempts by 48 pairs failed to hatch. Predators probably caused about 10% of egg failures. Only three of 49 chicks probably survived t o adulthood, indicating a juvenile mortality rate of about 94%. Predat ors killed at least 8% of chicks, 45% of juveniles, and possibly as ma ny as 60% of all young kiwi. Ferrets and dogs were the main predators of adult kiwi, possums and mustelids were the main egg predators, whil e stoats and cats were largely responsible for the deaths of young kiw i. Population models show that northern brown kiwi are currently decli ning at 5.8% per annum. This decline could be halted by cutting the cu rrent predation rates on young kiwi by about 34% to 33%.