Quantifying climate change impacts emphasises the importance of managing regional threats in the endangered Yellow-eyed penguin.

Climate change is a global issue with effects that are difficult to manage at a regional scale. Yet more often than not climate factors are just some of multiple stressors affecting species on a population level. Non-climatic factors-especially those of anthropogenic origins-may play equally important roles with regard to impacts on species and are often more feasible to address. Here we assess the influence of climate change on population trends of the endangered Yellow-eyed penguin (Megadyptes antipodes) over the last 30 years, using a Bayesian model. Sea surface temperature (SST) proved to be the dominating factor influencing survival of both adult birds and fledglings. Increasing SST since the mid-1990s was accompanied by a reduction in survival rates and population decline. The population model showed that 33% of the variation in population numbers could be explained by SST alone, significantly increasing pressure on the penguin population. Consequently, the population becomes less resilient to non-climate related impacts, such as fisheries interactions, habitat degradation and human disturbance. However, the extent of the contribution of these factors to declining population trends is extremely difficult to assess principally due to the absence of quantifiable data, creating a discussion bias towards climate variables, and effectively distracting from non-climate factors that can be managed on a regional scale to ensure the viability of the population.

Evidence for high inter-generational individual quality in yellow-eyed penguins.

Longitudinal studies focusing on lifetime reproductive success (LRS) have been used to measure individual breeding performance and identify commonalities among successful breeders. By extending the focus to subsequent generations we identify a proportion of high-quality individuals that contribute disproportionately to the population over multiple generations. We used 23 years of yellow-eyed penguin (Megadyptes antipodes) breeding data from one breeding area to identify the proportion of individual birds that raised successful breeders, which in turn raised offspring. We explored which life-history components influenced LRS, as this knowledge would enable conservation resources to be focused on high-performing individuals in this endangered population. From 2,147 birds marked as chicks, 370 (17.2%) survived to adulthood and recruited to their natal location, of which 219 (10.2%) fledged offspring: 124 (56.6%) of the 219 birds produced offspring that recruited as breeders. Only 102 birds (4.8% of 2,147) fledged first-generation offspring that in turn fledged offspring (second-generation offspring, or grand-offspring). We found that ∼25% of the birds that survived to breed had above-average LRS as well as above-average numbers of grand-offspring, and were more likely to have produced first-generation chicks that recruited and also produced above-average numbers of second-generation chicks. Our findings suggest that there is a core of "super-breeders" that contribute disproportionately to the population over successive generations. Lifespan and age-at-first-breeding were correlated with LRS. We suggest that traits of birds relating to longevity, health (e.g., immunocompetence) and fitness could be examined to identify potential links with high LRS and inter-generational fecundity. "Super-breeders" appear to consistently achieve high LRS and long lifespans in a stochastic environment, demonstrating greater resilience in the face of extreme events.

Effects of artificial social stimuli on the reproductive schedule and hormone levels of yellow-eyed penguins (Megadyptes antipodes).

The effects of social stimuli on avian reproductive behaviors such as breeding schedules and courtship behaviors are well known due to numerous field studies. However, studies that have simultaneously examined the effects of social stimuli on reproductive behavior and the mediating endocrine mechanisms have been largely restricted to captive populations, which may not be representative of free-living populations. This study, conducted over two breeding seasons, aimed to simultaneously measure the effects of experimentally increasing auditory stimuli on the breeding schedule and endocrinology (levels of total androgen, estradiol, progesterone and prolactin) on free-living yellow-eyed penguins (Megadyptes antipodes). The yellow-eyed penguin is the least colonial of all penguins, nesting far apart from each other under dense vegetation, and, therefore, is presumed to experience much lower levels of social stimuli than other penguins. Egg laying was significantly more synchronous and tended to be earlier when birds were exposed to playbacks of the calls of conspecifics in 1 year of the study. We also found that levels of total androgen and estradiol of males in 1 year, and prolactin in another year, were proportionally higher among treated birds compared control birds that received no artificial auditory stimuli. These results show that even among supposedly solitary nesters, social stimuli could still play a role in influencing reproductive behavior and physiology. For the first time in free-living seabirds, we have demonstrated that behavioral responses to increased social stimuli are associated with hormonal changes.

Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes).

Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.