Comparative ecology of northern brown kiwi (Apteryx australis mantelli) in Tongariro National Park and Tongariro Forest Park, central North Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University
Biological aspects of calling, range size, roost choice, feeding ecology, and potential threats faced by Northern brown kiwi (Apteryx australis mantelli) are described for a 14 month study in two conservation areas in central North Island, Tongariro National Park and Tongariro Forest Park. In Tongariro Forest Park 73% of calls were made by males. The 3:1 ratio of male:female calls changed seasonally, with the proportion of female calls increasing over winter and spring. Total call rates also increased during these seasons. Between nights call rates varied irrespective of season. Temperature and rain accounted for 44% of this variation. During the night, calling behaviour was bimodal, with the majority of calls occurring in the first and last three hours of darkness. In winter and spring males called, on average, 20 minutes later than in summer and autumn. Thirty times more calls hour-1 were heard in Tongariro Forest Park than in Tongariro National Park. Density of kiwi was estimated to be 1 bird/km2 in Tongariro National Park, and 4 birds/km2 in Tongariro Forest Park. This suggests that call rates are not linearly related to the number of kiwi present in an area. Practical implications of this for the interpretation of kiwi call surveys are discussed. Home ranges of kiwi varied from 30.8 to 91.8 ha. Range size of paired females tended to be larger than those of paired males. The range of an unpaired male was significantly larger than those of the paired males and paired females. Female home ranges overlapped more than male home ranges. Kiwi varied considerably in their choice roost. Roost type was dependent on habitat type. Roosts associated with fallen trees and surface roots were the most frequently used type. Kiwi infrequently used one roost site more than once, those roosts that were reused were large burrows of unknown size. Male kiwi used surface vegetation more often than females, while the females favoured roosts associated with hollow logs, and/or roots. Territory size may be a consequence of habitat. During 14 months of sampling, higher numbers and greater taxonomic diversity of invertebrates was found in Tongariro Forest Park than in Tongariro National Park with 55% of taxa common to both areas. Seasonal changes in the taxa found in faeces reflected seasonal changes in apparent invertebrate abundance. Kiwi also appeared to focus on a particular taxon, suggesting that they are selectively opportunistic feeders. Mammalian predators pose a major threat to the long-term survival of kiwi in the central North Island. Predator surveys indicated possums, cats, dogs, and stoats were present in Tongariro Forest Park and Tongariro National Park. A ferret was caught in Tongariro National Park, and pigs were observed only in Tongariro Forest Park, but probably ferrets and pigs are present in both sites. No significant difference was found between the numbers of stoats trapped in the two study areas. Local morphometric variation appeared to occur, with adult male stoats collected in Tongariro National Park being larger, on average, than their counterparts collected in Tongariro Forest Park. There were differences between areas in the average size of prey items with the average size of prey being larger in Tongariro Forest Park than in Tongariro National Park. Future conservation and management issues for Northern brown kiwi are discussed.