Document Type



Master of Science



Date of Defense


Graduate Advisor

Patricia Parker, PhD


Robert J. Marquis

P. Dee Boersma


Populations of Humboldt penguins (Spheniscus humboldti) in Peru began declining significantly in the 19th century because of industrial guano mining and a later increase in fishing. Guano mining changed the features of the penguins’ breeding habitat by eliminating the substrate where this species excavated their burrows. We analyzed the effects of nest and nest site characteristics and monitoring methodologies on Humboldt penguins’ breeding performance at Punta San Juan, Peru. We used a binomial generalized linear mixed model with random intercept to tests for differences in the probability of successfully raising at least one fledgling and also tested for differences in the number of fledglings produced among nests with different characteristics. We identified nests (including artificial nests) and classified them by nest cover (covered or uncovered), nest site habitat (cliff tops and beaches or caves) and nest substrate (guano or other substrate). We also assessed the impact of invasive and noninvasive nest monitoring methodologies on breeding performance. We included year and breeding season as random effects to account for environmental oscillation between and within years. Our results showed that the combination of guano substrate with noninvasive nest monitoring and nest cover were best correlated with penguin breeding success (increased probability of success and number of successful fledglings). The mean number of fledglings produced changed significantly between years and breeding seasons. In a separate analysis, breeding success of artificial nests was similar to natural covered or uncovered nests. Artificial nests in guano substrates were more successful than artificial nests in other substrates. Breeding success between habitats was similar. Our results show that nest and nest site characteristics affect Humboldt penguins’ breeding performance. Management decisions regarding penguins breeding habitat can affect the conservation of Humboldt penguins. An experiment is required to disentangle the effects of monitoring methodology and substrate on Humboldt’s penguins’ breeding performance, but as cautionary measures we recommend careful nest monitoring and avoiding guano extraction from penguins’ breeding sites.

OCLC Number