Determining the drivers of yellow-eyed penguin/hōiho (Megadyptes antipodes) productivity
|dc.contributor.advisor||van Heezik, Yolanda|
|dc.contributor.author||Young, Melanie Jane|
|dc.identifier.citation||Young, M. J. (2014). Determining the drivers of yellow-eyed penguin/hōiho (Megadyptes antipodes) productivity (Thesis, Master of Science). University of Otago. Retrieved from http://hdl.handle.net/10523/4711||en|
|dc.description.abstract||Seabirds are dependent upon marine systems for foraging, dispersion and migration, and on terrestrial systems for breeding, courtship and moulting (McKinlay 2001; Diamond and Devlin 2003). Long-term population studies of seabirds have made it possible to determine the trends in seabird productivity with respect to stochasticity in the marine environment. In this study, 28 years of yellow-eyed penguin/hōiho (Megadyptes antipodes) data were analysed to determine potential drivers of productivity and chick mass in coastal Otago, New Zealand. Hatching rates, chick survival rates and scaled mass (at pre-fledge when chicks are c. 90 days old) were used to determine how breeding hōiho are affected by perturbations in the marine environment in three separate breeding regions on the Otago coast. Using generalised linear mixed models (GLMM), the relationship between sea surface temperature (SST) at two scales, as well as the Southern Oscillation Index (SOI) were determined for each of the hōiho reproductive parameters at lags up to 18 months prior to breeding. In addition the instantaneous effects of weather were included in the models created to account for any additional climatic noise within the breeding season. A subset of data were omitted from the modelling process to determine the predictive capacity of the models, and correlations between these predicted and observed reproductive values were weak (Spearman’s rho: -0.64 to 0.54, p = NS). No single environmental predictor was indicated as a potential ‘driver’ of productivity; system complexity, and the many aspects of climate and weather, the influence of non-climatic processes, as well as the methods chosen, may have obscured a potential environmental predictor of hōiho reproductive success. Fluctuations in the observed reproductive parameters were attributed to the effects of mustelid predation and novel diseases; however the availability of food, both quality and quantity, was thought to be responsible for lower chick survival and mass in some years, and these observations are congruent with prior research (van Heezik 1990ab, 1991). There were clear regional differences in the reproductive parameters, with hōiho in North Otago consistently producing high numbers of quality chicks. Hōiho have adapted to having a reliable foraging area in close proximity to their breeding grounds, and the reproductive strategies they employ, including synchronous hatch of eggs, equal brooding and feeding of chicks, allow for productivity to be maximised, often in spite of adverse environmental conditions, because this closeness may allow for adult hōiho to buffer poor seasons with increased foraging effort without compromising their own survival (Darby and Seddon 1990; Edge 1996; Mattern et al. 2007). The data indicated that extreme inter-decadal La Niña events affect all hōiho breeding parameters, but the models did not always explain variation in these reproductive parameters at other intervals. Monitoring of the Southern Oscillation Index may allow conservation managers to avert chick starvation events in some years, particularly in North Otago and the Otago Peninsula.|
|dc.publisher||University of Otago|
|dc.rights||All items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.|
|dc.title||Determining the drivers of yellow-eyed penguin/hōiho (Megadyptes antipodes) productivity|
|thesis.degree.name||Master of Science|
|thesis.degree.grantor||University of Otago|
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