Kakapo habitat selection on Hauturu-o-toi in relation to plant phenology

Kakapo (Strigops habroptilus) breed only when certain gymnosperm species produce unusually abundant mast seed crops, events that can occur up to 5 years apart. Kakapo were first translocated to the offshore island refuge of Hauturu-o-toi (Little Barrier Island) in 1982. Despite the absence of known breeding triggers, several breeding attempts did occur prior to the birds’ removal in 1999. Although kakapo were reintroduced to Hauturu in 2012, the question of what triggers them to breed there remains a mystery. This paper re-examines unanalysed datasets to explore the link between kakapo habitat selection and plant phenology patterns on Hauturu during the 1990s. By comparing plant phenology with breeding attempts, we provide insights into potential breeding triggers, and the potential future of Hauturu as a sustainable refuge. We also provide an account of plant phenology patterns occurring on Hauturu. Resource selection ratios were calculated to determine habitat selection preferences using kakapo location data and a vegetation map of Hauturu. Analysis of plant phenology within preferred habitats was then undertaken to determine potential breeding triggers using a dataset of over 70 plant species collected from 1991–1995. Female kakapo that attempted to breed on Hauturu preferred Agathis australis (kauri) dominated vegetation to any other vegetation type. Phenology patterns coincided with kakapo breeding attempts, and attempted breeding years on Hauturu were years with high A. australis female cone abundance. The association between A. australis and breeding suggests that A. australis cone production could trigger kakapo breeding on Hauturu. With an increasing kakapo population and a limited number of suitable refuges, understanding the potential reproductive productivity of kakapo on Hauturu will be vital for their future management and recovery.