Resource partitioning between two competitive species, the hihi (Notiomystis cincta) and bellbird (Anthornis melanura), during the non-breeding season on Tiritiri Matangi Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
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Date
2012
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Massey University
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Abstract
Understanding the level of competition and resource partitioning between New Zealand’s ecological honeyeaters is important for hihi (Notiomystis cincta) conservation
management. Hihi management on Tiritiri Matangi Island has been thought to be
hindered by competition with bellbirds (Anthornis melanura), particularly at the
supplementary sugar water feeders. With some inconsistent results in differences between
their foraging ecology at different locations and seasons, I collected data on the foraging
ecology of both hihi and bellbirds on Tiritiri Matangi Island to compare with previous
studies at other locations. Nectar was the main constituent of both species diet with fruit
only being consumed in the autumn-winter months for both species. The main difference
between the species was that hihi consumed more fruit than bellbirds and bellbirds
consumed honeydew. Bellbirds foraged more in the higher vegetation layers and on
higher nectar value flowers than hihi which corresponded with previous studies. This
suggested that resource partitioning is likely to be in the form of bellbirds defending the
best resources of higher nectar value in the higher vegetation layers with interference
competition and hihi obtain resources with exploitation competition by utilising flowers
which are often smaller, less abundant or produce less nectar in the lower vegetation
layers. Male bellbirds and hihi were the most frequent visitors to the supplementary
feeders. With few interspecific interactions it suggests that male bellbirds are unable to
defend the feeders due to the feeders being overwhelmed with hihi and also showing how
dependent hihi are on supplementary feeding. Female bellbirds were the least frequent
visitors suggesting that intraspecific competition is greater at the feeders but only for
bellbirds as there was little evidence of high competition between the hihi sexes. There
may be some resource partitioning between habitat types as hihi were consistently found
at higher densities in the mature forest habitat likely due to their dependence on the
feeders and artificial nest boxes, whereas bellbird densities changed with resource
availability and breeding season territoriality. The densities of both species were affected
by the presence of feeders and nectar availability with positive correlation between the
species in the non-breeding season, suggesting that hihi habitat preference was not
affected by competitive exclusion from bellbirds. The removal of 100 bellbirds for a
translocation had no evident impact on hihi and bellbird densities at capture sites.
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Keywords
Stitchbird, Hihi, Notiomystis, Bellbird, Korimako, Anthornis melanura, Resource partitioning, Forest birds, Competition, Habitat, Ecology, Conservation biology, New Zealand, Tiritiri Matangi Island