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    Whisker stable isotope analysis used for proactive management of recolonising New Zealand sea lion population
    (Inter-Research Science Publisher, 2023-10-26) Chilvers BL
    New Zealand sea lions Phocarctos hookeri have experienced a 46% decline in pup production in the last 25 yr, driven by female deaths in trawl fisheries around the Auckland Islands. The only colony for this species recorded away from the subantarctics and this fishing impact is on Stewart Island. Despite the Stewart Island colony only being 1% of the species, it is significant, as it is currently the only stable population and is located in an area away from most on-land human impacts, although not away from potential fisheries pressures. To ensure this colony’s persistence, more information is needed on these sea lions’ diet, foraging behaviour, and local fisheries interactions for management that promotes their protection. The present research investigates the long-term foraging behaviour, and infers the diet, of female New Zealand sea lions on Stewart Island using their known foraging behaviour and linking this to their proximal and full-length whisker stable isotope values. Previous foraging studies found that these animals have small foraging areas with consistent mesopelagic diving behaviours. These behaviours, linked with their whisker stable isotope values, show consistency in foraging behaviour and in - ferred diet across their entire adult life. Currently, there are no known commercial fisheries bycatch issues for sea lions around Stewart Island. However, precautionary measures ensuring fisheries pressure does not increase and management to safeguard that deepwater trawling and finfish aquaculture remain absent would be proactive steps that should be undertaken for the protection of this new colony and for this Endangered species as a whole.
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    Tactile senses and foraging in birds, with emphasis on kiwi : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2010) Cunningham, Susan Jane
    Probe-foraging birds must often rely on senses other than vision for prey-detection. One such sense is ‘remote touch’: the detection of vibration and pressure cues from prey within the substrate. Remote touch is mediated by the ‘scolopacid-type bill-tip organ’, which consists of a honeycomb of sensory pits in the bill-tip, containing clusters of mechanoreceptors. This organ was originally described in the neognathous shorebird family Scolopacidae, but was recently also discovered in paleognathous kiwi (Apterygidae): an example of convergent/parallel evolution. My aim was to discover how widespread this organ is among birds, compare its anatomy and function in foraging between kiwi and other probe-foraging birds and elucidate in detail the foraging behaviours and senses used by free-living kiwi. Within the thesis I compare the bill-tip organs of kiwi and shorebirds using material from the brown kiwi (Apterygidae: Apteryx mantelli) and bar-tailed godwit (Scolopacidae: Limosa lapponica). I provide the first description of the organ in a third family of birds, the ibises (Threskiornithidae), and give evidence that it may exist in simplified form in a fourth family, Rallidae. The Scolopacidae, Apterygidae, Threskiornithidae and Rallidae are widely separated on the avian phylogenetic tree. This suggests that the evolution of the scolopacid-type bill-tip organ and associated sense is favoured by a probe-foraging lifestyle. Foraging trials confirm the bill-tip organs of brown kiwi and Madagascar crested ibises (Lophotibis cristata urschi) are functional for remote touch. The ibises rely solely on remote touch to find buried prey, whereas brown kiwi use the sense in conjunction with olfaction. Free-living brown kiwi display no obviously visually-guided behaviours, instead using hearing (head-lifting in response to noises audible to the observer), olfaction (odour sensing behaviour, ‘sniffing,’ in the direction of these sounds) and touch. Kiwi tap ahead with their bill-tip when walking and move their facial bristles forward when foraging, forming a ‘net’ on the ground. The bristle follicles in kiwi (and some other insectivorous bird species) are innervated with Herbst corpuscles, suggesting tactile function. Female kiwi probe on average 30% deeper than males and juveniles, but there are no other differences in foraging behaviour between the sexes.
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    Abundance and foraging niches of forest birds in part of the Ruamahanga Ecological Area, Tararua State Forest Park : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1989) Moffat, Michael
    To test the applicability in New Zealand of ecological theories derived from the study of northern temperate and tropical avifaunas, the bird community in part of the Ruamahanga Ecological Area, Tararua State Forest Park was studied from October 1982 until February 1985. A modified five-minute bird count to determine the relative abundances of each bird species with a near/far ratio proved useful in assessing the distribution of the common bird species but was inadequate for the rarer species. Twenty-nine bird species were seen, twenty-one of which probably bred within the study area. Eleven forest bird species were seen with sufficient frequency to apply the near/far. Bird species diversity was significantly correlated with foliage height diversity, but not with plant species diversity. Principal component analysis was used as a graphical tool to describe the inter-relationships of bird species distribution with plant species and plant structure in greater detail. Bird species composition was related to both the forest structure and the plant species composition. The distributions of ten common bird species were positively correlated with high canopy forest, five species with red beech-doninated forest and five species with podocarp/broadleaf-dominated forest. Many of the bird species were most abundant at the end of the breeding season in February-March. This was not apparent from consideration of the five-minute bird counts alone because of seasonal changes in conspicuousness. The modified five-minute bird counts were useful indicators of bird movement into and out of the study area. Only whiteheads shoved consistent seasonal changes in altitudinal distribution, higher in summer than in winter. By determining the relative importance of foliage height, tree species and substrate bird species foraging niches were examined. Foraging site showed the greatest difference between bird species, followed by tree species and then foraging height. Comparison with other studies showed that there is a large degree of plasticity in foraging niche site between habitats in New Zealand birds. Foraging niches of congeners in Australia and New Zealand were similar. Each bird species preferred different species of trees for foraging. In winter decreased foraging niches overlaps were observed in conjunction with mixed species flocking. Studies of New Zealand birds indicate that foraging niches are sufficiently plastic for forest conservation management strategies be considered on a forest by forest basis. The plasticity of foraging niches may also account for the small proportion of introduced birds in the study area. Competition is probably important in structuring the forest bird community. Both niche breadths and niche overlaps were comparable with studies on much richer bird assemblages. Introduced birds were largely confined to forest margins and to resources which were previously used by extinct native birds, suggesting that the remaining native birds are successfully excluding introduced birds.