The importance of niau (Rhopalostylis baueri) in the diet of the Tasman parakeet (Cyanoramphus cookii) in the Norfolk Island National Park

Abstract

ABSTRACT The behaviour and diet of the Tasman parakeet (Cyanoramphus cookii) have not been quantitively described. We quantified the relative frequency of behaviours and diversity of food items for the species during autumn and winter to help refine the current management of the species. We also collected information on the availability of one of their main foods: niau (Rhopalostylis baueri) fruits. Parakeets fed on fruit pulp and seeds of eight plant species. Niau fruits represented 44% of total feeding bouts indicating that this is an important food item during the autumn-winter period. The most common behavioural state during our observations was feeding (30% of behavioural states). Our estimate of niau fruit availability in the core area of Tasman parakeet occurrence indicates approximately 1.2 million fruits during the peak of fruiting in spring. Tasman parakeets are generalists, but niau fruits represent an abundant and important resource. Although niau are common and produce large quantities of fruit, introduced rats (Rattus spp.), potentially represent significant competitors to Tasman parakeets, because they also feed on niau fruits. Ongoing control of rats is thus critical to maintain large quantities of native fruits to sustain a growing population of Tasman parakeets.