Foraging ecology of the world's only population of the critically endangered Tasman parakeet (Cyanoramphus cookii), on Norfolk Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Auckland, New Zealand
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Date
2016
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Massey University
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Abstract
I studied the foraging ecology of the world’s only population of the critically
endangered Tasman parakeet (Cyanoramphus cookii) on Norfolk Island, from July
2013 to March 2015. I characterised, for the first time in nearly 30 years of
management, the diversity of foods consumed and seasonal trends in foraging
heights and foraging group sizes. In addition to field observations, I also collated
available information on the feeding biology of the genus Cyanoramphus, to
understand the diversity of species and food types consumed by Tasman parakeets
and their closest living relatives as a function of bill morphology. I discuss my findings
in the context of the conservation of the Tasman parakeet, specifically the
impending translocation of the species to Phillip Island. I demonstrate that Tasman
parakeets have a broad and flexible diet that includes seeds, fruits, flowers, pollen,
sori, sprout rhizomes and bark of 30 native and introduced plant species found within
Norfolk Island National Park. Dry seeds (predominantly Araucaria heterophylla) are
consumed most frequently during autumn (81% of diet), over a foraging area of ca.
90 hectares, at 6.94 m above the ground. During winter, consumption of dry seeds
remains high (61%) however over less than half the foraging area of autumn (46
hectares). More importantly, foraging height during winter is significantly lower than
any other season, at 2.16 m. Though overall 18% of all foraging registered occurs at
ground level, the highest frequency occurs during winter (55.4%). I argue that this
seasonal shift in foraging area and height has important consequences for the
management of Tasman parakeets. In particular foraging close to the ground within
a small area makes the world’s only population of Tasman parakeets highly
vulnerable to predation by introduced cats, thus intensification of cat control during
this period is crucial for safeguarding this species in situ.
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Keywords
Cyanoramphus, Cyanoramphus cookii, Tasman parakeet, Food, Endangered species, Norfolk Island, Research Subject Categories::NATURAL SCIENCES::Biology::Terrestrial, freshwater and marine ecology::Ethology and behavioural ecology